75F is OK for the bottom and one side high up. The hot zone needs to be 95 to 100F. Ive had large adult igs who loved to bask in 105F and even higher. I used to watch that closely, using a laser thermometer to measure his skin temp on top, where the heat fell. But they never hurt themselves, and they always limited the length of time they basked at that temp. Also, he'll live longer because of the exercise he will get as he roams the cage.\
Measure the ambie nt temp of the warm side by pointing the laser at something substantial, like an iguana. A reading of 95 on an ig's skin will read 140 if pointed at a piece of paper in the hot zone.