They usually suggest that your uth should cover approximately 1/3 of your floor space. A 32 qt tub is about 24x16 -- so ideally you would want a uth that is 8x16 approximately. I'm not sure what size the zoomed or other heat mats come in.

I use flexwatt -- which you can get from reptilebasics.com It is sold by the foot, and Rich will wire it for you so all you have to do is hook it up to a thermostat and plug it in. It is also considerably cheaper than a heat mat -- even with the shipping.

Oh yeah...I am using 1 foot of 11" flexwatt on my tub (yeah, I know -- that's about half of the floor space. I suppose you could use 4" flexwatt, or two strips of 3" or 4"? (placed side by side?).

The main reason the "experts" say to only cover 1/3 of the floor space is in case of a thermostat failure then your snake has a cool place to escape to.

Hope this helps....