This is what I do a well. Admittedly, I am new to air gunning. Have you encountered any issues with the PCP, seals, etc. with a max filled tank and stored?
I have watched YT videos on increasing the FPS on Dan Wesson revolvers. These seem the most straightforward to adjust power. On the other hand, a Dan Wesson .357 with 8" barrell should do ~500 FPS with the right pellet.