Walther Reign bullpup regulated ?

I had to increase HS to get any power out of my Walther Reign .22 , I'm at 37fpe with NSA 17.5gr I only fill to 2,700psi. Pointless to fill any higher. The HS is to light still. A regulator would be awesome.
I had to increase HS to get any power out of my Walther Reign .22 , I'm at 37fpe with NSA 17.5gr I only fill to 2,700psi. Pointless to fill any higher. The HS is to light still. A regulator would be awesome.
How hard is it to increase hammer spring in the Reign?