Well theres not a lot i can add mate. i LOVE the theory with the layout just not the choice of forground plant. it's too tall. (awesome quality though, top marks for lushness - if thats a word)
dont you dare touch the java fern - that is by far the best specimin i've ever seen. if it's too tall buy a bigger tank. seriously mate it's taken ages to grow to that size. would be like chopping the top off an oak. leave it be.
if you change the sag for something shorter (glosso's a good option) it'd put the fern back into perspective.
I have a vision of an english country medow, open grass land, neat from grazing cattle with a massive 500yr old oak tree in the corner.
you could recreate that image in miniture in your tank very easily. just replace the cows with fish.
Definatly need to move the crinium (i know i may be biased on that point but it's a bit busy wherever you put it.)
i'd leave the background as is, if you do get the glosso into a good heavy carpet it will draw your eye to the forground and the fern will sillouette (SP?) against the black wonderfully.
the problem at the moment is the sag's getting too tall. where you can see the gaps between the leaves your eye looses the continuity of a good carpet and the picture breaks down rather.
a bit like the english medow without the cows, grass gets out of control, turns to hay and gets overgrown.
the sags definatly the problem not the fern IMO. other than that awesome quality as usual, stunning colour in the sag, absolutly flawless. no spots, torn leaves, tiny hair algae strands, the odd holey leaf........ nothing. pure quality in a box