Situation. Dilema. "A conundrum, if you will..."

I already have the smaller of my two snakes in a tub. I'm switching the larger one over this weekend. I want to stack the tubs, but I don't have a rack. Well, I'm a chick, I have one, but y'know...

My question is: How can I separate the tubs so that the heat pannel for the upper tub isnt laying on the roof of the lower tub? Do I even need to, since heat rises?

Suggestions needed. Thanks,
Haylee