"You would probably be better of doing a leak down test instead of a compression test. By doing the leak down you would find which cylinder has the bad gasket area or crack in the head etc."
Maybe I am reading this wrong but it sure seems to me you are trying to say he should do a leak down test because a compression test will NOT show him what cylinder is bad.
"As for the bubbles in the radiator a leak down test would tell you which cylinder the bubbles come from so you then know where to better look for cracks"
There it is again. Use a leak down test to find the cylinder with the problem.
You do not really think a leak down test is any better than a compression test at pinpointing a problem in a cylinder and telling you what cylinder the problem is in. DO YOU???????????