From what you describe you should be fine stacking them as long as you have a t-stat or dimmer controlling the temps. Keep the hot spots on the same end.
Ya I'm just going to get one dimmer for now (temporary) so I thought if I stacked the tubs I wouldn't need to get a second dimmer since Monty is located on the other side of the room from where Candice's tank is.
You could certainly try it and see how the stacking affected the temps in the top two tubs - just be prepared to need to get extra dimmers if the top tubs get too warm or anything.
It's just easier to have the $20 or so set aside then not need it rather than the other way round.
dr del
Derek
7 adult Royals (2.5), 1.0 COS Pastel, 1.0 Enchi, 1.1 Lesser platty Royal python, 1.1 Black pastel Royal python, 0.1 Blue eyed leucistic ( Super lesser), 0.1 Piebald Royal python, 1.0 Sinaloan milk snake 1.0 crested gecko and 1 bad case of ETS. no wife, no surprise.