Upper Radiator Hose Pressure??

Pressure test the cap!
If it relieves at 15 or less, it's all good. The system pressure cannot exceed the relief valve. If the valve does not relieve, the pressure will find a way out.And it won't be pretty. Nor convenient!

FWIW; I run 7psi caps in all of my older cars, with mechanical fans. The hoses last forever, and the rads never develop leaks.