I think you're asking for problems doing it this way. Unless you have a thermostat for each tub, you run the risk of run-away temps. Go buy a shelving unit at Home depot and set up a cheap rack. This would be better than overheating your snakes.
Sure, some can make an argument for this being safe, but I bet no one can give you a money back guarrantee.
I do not like having heat above and below every tub, except the very top tub. An overheating problem could easily become a problem, one that could kill a snake or two before you could catch it.
Your mileage may vary,
Jim smith