Our experiences point more to 'flow' than 'pressure'. We found that even with 60+ psi pressure, if we were using a 1/2" hose, we may still not get a good shower.
We use a Watts whole house regulator. It's 3/4" diameter and it's set to 50psi. We also changed over to 3/4" hose. And we removed the water restrictor that's in the head of the shower head.
If you can't get past your built in regulator, you might consider bigger hose diameter and removing that restrictor from your shower head.
2017 CC38EL Silverado 3500HD