Brainstorming ideas for coolant crossover on Air-Gap intakes

Yeah at 5000ft you need all the air you can get, and the colder, the denser.
If you are having a hot kick-back on the starter,at 5000ft, with 10.5 Scr,and 8* initial; the kb might not be compression.

I ran my 367 with a 223* cam, at 11.3 Scr(aluminum heads), and at 900ft, with 14* initial. With the mini-starter I had no issues, even at 205* minimum running temp.
So perhaps one or more of the parameters are off.
The biggie would be your elevation.
For example; correcting 10.5Scr for 4000ft your Dcr might be 7.92/158psi.
And at 900ft I get;8.54/174psi, at 59* ICA.
So maybe verify your local elevation. I got the 5000 off the net, so who knows if that is correct!