Stand gaps and uneven water levels

I have some gaps on the short edges of a 2ft tank between trim and stand. Front edge okay but back I don't know as I can't reach behind (it's against a wall). I've shimmed to seat the corners as I thought that is the most important thing. True?
Started thinking of a tank I had a few years back, a model which has corner caps on the base, raising the glass off the stand. Went to my LFS today who have a few different sizes assembled of this model and slid paper and credit card thickness plastic under them. Apart from side gaps, I noted variances in gap heights and lengths on either side of the middle and, interestingly, on the long tanks (weighted) with substrate & decor (no water), the mid section touched the stand - is this a dangerous design that might cause tank breakage? Which would be surprising to get it so wrong on commercial tanks.
If my gaps are only on the short sides (30cm wide) plus as it's only a 2 footer anyway, should it really be a problem to have edge gaps if the corners are touching the stand? I've got a 25cm long cube supported only by 4 feet with the rest of the trim raised. Also, would a few millimetres off-level on two sides (front right and side back) as I drew in the attached picture cause twisting? When I test with water in a container, it angles toward the back right corner. Would this be a concern if it's only 3 millimetres on a tank? Thanks
Edit: forgot to say the cube tank with the feet and raised trim was made that way. I didn't add anything to it.

I broke a tank doing that when I first started keeping fish. It was a beautiful Odell. Here is my opinion, put your tank on a solid, level stand that is properly sized for your tank and its weight.

@Archerfish O’dell . There’s a name out of the past .

Archerfish said:

I broke a tank doing that when I first started keeping fish. It was a beautiful Odell. Here is my opinion, put your tank on a solid, level stand that is properly sized for your tank and its weight.

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I agree. I knew someone who had the same thing happen to them. Right size stand is a must.

Archerfish said:

I broke a tank doing that when I first started keeping fish. It was a beautiful Odell. Here is my opinion, put your tank on a solid, level stand that is properly sized for your tank and its weight.

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The Aquarium Home said:

I agree. I knew someone who had the same thing happen to them. Right size stand is a must.

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Oh, that's too bad about the tank.
The stand I'm using DOES fit width ways for the glass. The trim is a bit wide so hangs slightly out on either side. Length ways the stand is about 10cm longer on each side but I added reinforcements to hold the shelf up at the ends plus the middle of the tank that go right down to the ground. I just had trouble eliminating the gaps so I feel kinda stuck. I've heard store bought shelves can suffer the same problem or else are poor quality anyway (e.g. particle board). Mine isn't quality wood but I did reinforce it like I said. They're not gaping gaps. By the way, I saw a more expensive tank there which looked better quality and had a thin layer of felt-like material added to the base - it still wasn't perfectly level. I could slide a paper under one corner although it was a tighter fit. Overall it sat pretty level on the stand. The store has a concrete floor.
Thanks to every one for responding. I do hear what you're saying.

FishJourney said:

The trim is a bit wide so hangs slightly out on either side

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That's a no go for me. But what about a picture of what you are trying to describe ?

MaloK said:

That's a no go for me. But what about a picture of what you are trying to describe ?

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Regarding the gap, its about 1.5 millimetres. I wonder if the slight water imbalance is more the worry, if at all. Pics from #5 onwards is meant to show the water levels. I intend to fill the tank to 24-25cm high when ready.

MaloK said:

That's a no go for me. But what about a picture of what you are trying to describe ?

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Oh sorry, here's the trim. Hangs off one side a bit more coz I didn't centre it precisely enough. A couple of photos I took through the holes of the shelf posts to try to get a better shot lol.

FishJourney said:

Regarding the gap, its about 1.5 millimetres. I wonder if the slight water imbalance is more the worry, if at all. Pics from #5 onwards is meant to show the water levels. I intend to fill the tank to 24-25cm high when ready.

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You can get a roll of exercise mat from Kmart, cut it to size, and place it under the tank (photo below). That will address your concern.

FishJourney said:

Oh sorry, here's the trim. Hangs off one side a bit more coz I didn't centre it precisely enough. A couple of photos I took through the holes of the shelf posts to try to get a better shot lol.

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How much overhang is that? I wouldn't worry about it if it's only 2 or 3cm overhang.

FishJourney said:

By the way, I saw a more expensive tank there which looked better quality and had a thin layer of felt-like material added to the base - it still wasn't perfectly level. I could slide a paper under one corner although it was a tighter fit. Overall it sat pretty level on the stand. The store has a concrete floor.
Thanks to every one for responding. I do hear what you're saying.

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That’s most likely a locally made tank. The manufacturer recommends a polystyrene sheet (the white felt-like material) underneath the tank because the bottom glass sits flat on the support structure. Without the polystyrene, the bottom glass will crack if you accidentally have a grain of sand between the support and the bottom glass.

I agree, a good polystyrene sheet in enough to be perfectly safe.

TNG said:

You can get a roll of exercise mat from Kmart, cut it to size, and place it under the tank (photo below). That will address your concern.

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People say not to use them for trimmed tanks, only rimless or it can put pressure on the bottom pane of glass. Not sure the gap is something to worry about given its only on a 30cm wide side. King of DIY says mats don't address levelling, only irregularities which I took to mean bumps that the foam/mat can absorb like a pebble, sand grain etc before returning to a level line. But a depression in a board has a concave shape.
Not trying to be argumentative. I can't help having questions lol.

TNG said:

How much overhang is that? I wouldn't worry about it if it's only 2 or 3cm overhang.

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Trim width is just under 1cm longer than the board, making it less than half a cm overhang on each side. So that was my thought too.

TNG said:

That’s most likely a locally made tank. The manufacturer recommends a polystyrene sheet (the white felt-like material) underneath the tank because the bottom glass sits flat on the support structure. Without the polystyrene, the bottom glass will crack if you accidentally have a grain of sand between the support and the bottom glass.

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Sorry I wasn't clear. It was a very thin piece of material glued to the underside of the tank, nothing like a separate mat or foam.