I'm curing a few pieces of driftwood I found at a lake but they aren't sinking. To save money, I was wondering if instead of plexiglass or slate, I could use the front cover of a CD case and screw it to the driftwood for a base? If I cover it with a inch or so of gravel, will it hold my driftwood down? Also, will the plastic the cover is made of be okay for my fish? I'm planning on using stainless steel screws. Are they okay?