'68 Coronet R/T
Oldtimer
not a fan of Flexzilla because they have very thin walled aluminum fittings on the end and even using the right wrench its going to strip getting the coupler on the first time. The hi flow couplers I have bought are blowing out o rings constantly and have to keep getting changed, its down to needing vise grips to hold onto the hose. Nice flexy hoses, just not a fan of the ends.
As far as the gotta have CFM, I get it, but if you increase the size of your air hose, you are going to require more CFM to get the pressure up. I am sure its not going from 1/4-1/2. but you gotta have the compressor that can do it and you might just hear the compressor running more. I dont know if he has a 2.5 hp pancake tank compressor or a 50 horse screw. If you do not have the CFM, you will not keep that 30PSI consistent at the gun. When you lose the CFM, that pressure is going to drop.
If you don't have a compressor capable of producing the proper CFM to handle your equipment - you need a better compressor. PSI does not equate to CFM in any equation.