HELP Please! Which is less stressful??

[Argentra]

Ok, I have the tub with UTH on each side, background on the back and adhesive felt on the sides, and 5 holes soldered at the top of all four sides. Shown here:



So far so good? Here's the problem:
The warm side is around 92, the cool side around 82... but the ambient temp is around 75! How the heck... So I'm wondering how I might be able to fix that and make sure it's warm enough in there. Insulate the sides? The top? Close a few holes?

I'll be working with humidity once I get the temps ironed out.

[Ginevive]

I was going to recommend FW and a t-stat Mine keeps things spot-on in the temperature department.

[Argentra]

Both UTH are on stats, and I have no flexwatt. The side temps are great, but the ambient still won't go above 75...it's really confusing. I've heard that tubs keep temps really well, but this one is acting just like a tank. I even usurped my BF's nightstand (he's not happy about that) to put the tub on the warmest side of the room...