Possible to have different sized tubs in same rack?

[Trackstrong83]

I've raised numerous babies in 28qt tubs with no problems and they continue to be my best eaters.

My 41qt xpvc rack will take 28 or 41qt tubs

Awesome that's what I'll do then.
Do you use belly heat on all of your racks?
It's is my first time building a rack, so I'm not sure.