I know, I will not be getting my thermostat until Friday but until then I'd like to know if I should invest in a larger UTH. I'll give a little more details.

Unregulated my UTH went to 138 F before I shut it off. During this time the ambient temperature in the tank was 74-75. I want to stay away from getting a heat lamp as much as possible. I will not be using any form of insulation unless I have to. I will be using Aspen Snake bedding.

This is all on estimate/opinion basis. Do you think I should get a bigger UTH from your experience? Thanks.