[NLRS] Antenna height question

[Arliss]

I'm looking for advice on antenna height for antennas for 902 
through 10 GHz.

The ground around my home is level to downsloping out to a mile 
away in any direction.  However, pointing to the Twin Cities, the 
ground from 1 mile out to 15,000 ft away gradually slopes up to a 
maximum of 100 ft. above my ground level.  Beyond 15,000 ft. 
away, the ground is lower again.

I have two spots available on a tower for my 902 MHz - 10GHz 
antennas -- 72' and 112'.  Everyone around here knows the 
problems we can have with ice and wind, and from that standpoint, 
as well as just the ease in putting the antennas up and keeping 
them up, 72' is better than 112'.  But does anyone have any 
guesses as to how much I'll be giving up signal strength-wise if 
my antennas are 30' below a ridge that's 3 miles away instead of 
being level to slightly above the height of the ridge?

By the way, if my calculations are correct, if I'm at 72' on my 
tower, that 100' high ridge is less than 0.2 degrees above level.
And the approximate distance from here to the Twin Cities is 
about 200 miles.

I'm not expecting anyone can give me anything like an exact 
answer, just something along the lines of "10 GHz into the Cities 
will be pretty tough if you don't have the antenna above the 
ridge," versus "you'll never see/hear the difference between 72' 
and 112' on any of those bands."

Thanks & 73,

Arliss  W7XU