Looking to make about a half inch to inch of clearance. Im stacking a 4x2x1 tank on top of my 4x2x2 homeade tank. My home made one is very heavy and strong. Im using that as my bottom tank. But its ventilation is on the top. above that tank im putting my lighter PVC cage im purchasing. Like i said i wanna get some sort of adhesive legs or stubs on each corner of the pvc tank that are strong enough to hold it, so air can still flow through. I dont really wanna use cut up wood to make some clearance. I would rather some sort of rubber legs or little things to put on the bottom if you know what i mean. Hopefully i explained that correctly. thanks.