My first comment is tubs don't hold heat well at all I have no idea where that idea came from with out power they cool off very very quickly. I have a rack, glass enclosures, and custom plastic ones they each have advantages and disadvantages. Holding heat in a tub is really poor, my rack drops a degree every 10 min with no power my custom enclosure drops a degree every hour.

Where tubs heat fast and cool fast and cost more to heat (fast heat loss given equal wattage) a wooden enclosure is harder to heat but will hold heat better and longer. I still likely recommend a tub over a custom wood enclosure as the UTH is problematic and RHP (the easy solution) are costly.

I prefer to make sure air is moving so I place holes at the top edge of the tub over the cool end and lower on the side on the hot end. This ensures air will circulate through the space and not just stratify. I like holes about 1/8 inch or a bit bigger and the amount is variable. If you are getting lots of condensation you don't have enough if it is too dry and drys quickly then there are too many.

Removing then once stuck can be done carefully but they can also be damaged trying. Some people will use aluminum tape over the sticky part of the pad and then tape it (aluminum tape) to the tub. Yes the pad can be stuck to the tub as long as you have a T-stat to keep the temps correct for the snake there is no way at 90ºF the tub will be damage. Make sure you have a little air space under the tub to allow heat to dissipate some, don't place it directly on something and then the tub on it, heat will build up to dangerous temps.