In addintion to the binder clips, I was using bungee cords on mine. But, I switched to those luggage straps which look better IMO.
Also, depending on where you live, if you have high ambient humidity, you may need to get a fan to circulate the air in the tubs to keep the humidity down.
As for tub sizes, I have my yearling in a 32qt, my 2 y/o in a 41qt, and my 5 y/o in a 60qt. It basically has the same floor space as his 50gl tank. Just not the height. I've only had him in there for a couple of weeks so I'll see how it goes...
Rob