I'm not sure about that tub... Wheels? That sounds like a recipe for disaster. Not to mention, cleaning the bottom is going to be a pain in the ass. Also, I'm not sure if those gaps on the bottom will distribute heat properly, someone else would have to comment on that. I would say ditch it and find something better. Most stores will have similar sized tubs for $4-6.

The second placement of the UTH is the better placement. The first placement may make the cool side too warm.