Thanks everyone for your input. It looks like 6ft long is becoming the more popular choice. I think that's what I'm leaning towards also. Now the question is if 36" is wide enough for me, or should I go for 48". The main reason I wanted to keep it 300gals or less is so I didn't have to upgrade any of my current equipment (except lights of course). But, I may consider doing 72X48 anyway. This is likely the last tank I'm going to buy for a long time, so I might as well go as big as space and money will allow.