Plywood top of stand how thick should it be?

Awesome, yes the ply reaches the end of the 2x4 right up to the edge, and the tank will be right up to the edge on the back and front also, the sides the ply will be 5" longer but this reaches the rim of the 2x4 also, maybe a layer of thin foam say couple of mm inbetween tank and ply.

 

from your build thread it looks like a rimless tank?

 

That is correct

 

from the looks of your stand build, weight should be distributed pretty evenly. Sorry I jumped the gun on my first post, I thought there were no 2x4's directly supporting the tank at the time.

 

No problem, the tank corners at the front will line up with the plywood on the front left edge when seated, so the corners will not be resting on the upright 2x4s, is this still ok?

 

it should because the top frame will equally distribute weight to your 4 upright "legs"

 

Brilliant, thats put my mind at ease, what about the foam

 

I like the idea of using a thin piece of foam under rimless tanks

 

Definitely put in some cross braces throughout the frame (id use 3). For the plywood, I would use 1/2 inch marine grade if you have it just because i like to overbuild a bit (3/4 is ok too). Contact your manufacturer to see what they recommend about the foam. I know some companies require it for warranty, and some it voids.

Rimless are scary that way.

 

1/4" luan on the back should help prevent racking too. That's what I've done on the 4 stands I've built.