Im def. going to use pond armor to seal and I am going with a 10'x4' tank, I will order all the plywood 10' pieces and my stands just need to be cut down to 3' of the ground and re- bolted and bring out two more feet for the width,so the stand is easy. I will get a quote for a 9' viewing glass 3/4 thickness saphire glass. next we have to talk about filtration, which needs to be powerful and I want a drip system. Should I use a 180 gal for the sump, should I place underneath? or to the side?You should consider the shape and the space, if your talking 8+ feet in any one direction then you need more then 1 sheet for the bottom of the tank. For 2 sheets your foot print could be 16x4 or 8x8. Both of those would give you same volume however the glass is going to be much different price. During my research I found most people agree the easiest way to seal would be pond armor, however, a much cheaper but much more headache would be 3m Bondo resin and hardner.