I'm gonna try to do a leak-down test in the next day or two, I would assume if the head gasket is causing the problem it should leak air out the collant passages. I've seen higher pressure rated radiator caps, like 30 pounds, on ebay. Hrmpf!!! Have to wait till I do a lead-down to see.

A leak down test will not always find a leaking head gasket.  Sometimes it takes  500 psi or more to flex the head like it does when the engine fires to make the head gasket leak.  Your radiator and hoses will not take 30 pis very long.