[Zero10]

I do a leakdown test for 10 or 15 seconds, long enough for the reading to stabilize.

Wow, 10,200 feet, that's pretty darn high up. Honestly, seeing 100psi on a compression gauge scares me, but for your altitude, it would be about right!

If you do a hot, dry compression test, you should see effecticely 12:1 compression, or around 115psi. Please do let us know what you find, as I only recently adopted this idea of using math to determine expected compression values.