I have most of the same parts on mine. I had to tune it WAY down to get it to drop to ONLY 40 FPE with JSB 25.39 grain pellets. Step one would be to run it over a Chrony and tune from there. I have the lightest hammer spring available with the TSS, and it is literally just a couple threads from the bare minimum setting. At 40 FPE, it is quieter than factory stock.
My build.....
Huma Regulator for .25 caliber with integrated block for pressure gauge, adjusted to 1800 PSI (actual pressure, the knob on the regulator indicated a lower setting).
Hill valve, with optional very light 6 pound spring
Hill plastic transfer port, 0.187 internal diameter (ID).
Hill 25 gram hammer with lightest striker, pushed by the Twin Spring System (TSS) with lightest two springs available.
TSS, adjusted to minimum spring preload, with a very huge gap.
Barrel drilled 0.187 inch (deburred and polished the hole), to port match with the rest of the components (transfer port and valve).
Bolt, re-contoured to a spoon shape and narrowed at the transfer port (so the bolt blocks less of the transfer port hole)