I want to make a rack / stand (double tank - top and bottom) for a club auction donation. What is the most preferred combo? 55g/55g, 55g/75g, 40g/40g, four 10's, 50 2.5's, 750g/500g ? The last 2 - forget about it, it won't happen! The next few days at work will be slow and I'll have some time to...