Safe temperature to set my heat mat to if I don't have an infrared thermometer?

[Bodie]

I did use an IR gun... most of the readings came out between 88-92 degrees, so brought my "blank temp" down by 1 degree.

I hear ya my man. If you are concerned about the accuracy of your IR gun, what jmcrook said earlier about using a glass of ice water to check to see if your IR gun is accurate is spot on. Make a glass, give it a few minutes to settle in and shoot it with your IR. It should read close to freezing. If it is way off, then I would get a new IR pistol.