the temps arn't going to be 100% constant across the heat tape, the middle part will be the hottest or close to it, heat tape is made with the cheapest heating elements you can possibly get, so don't expect much as far as consistency.
you really shouldn't care about the heat tapes temp unless its 110+. stick a tub in there, wait a bit and see what the temps are inside the tub. you may have to have your thermostat set for 98 degrees to have your tub be at 92.