Your UTH shouldn't get hotter than 94 IMO.
This is about right ^^
If you use a on/off thermostat follow it's cycle from on to off to back on again and try to make it so it's hottest point is about 94 degrees.
This should get you temps like:

78 cool end
86-87 warm end
90-92 directly on the hot spot.

Depending on how cool your rooms ambient temp is of course.

Let's see how it looks when you're finished