Just going to a softer spring will slow things down but will cause even more hammer bounce. Possibly lessening your shot count.
I bought the regulated model. Loud, hammer bounce was unbelievable, air consumption and shot count were terrible. My solution was to make a hammer debounce device (HDD). To lower the power you just change to a lighter spring in the HDD.
I made an extra that you can have if you want it. What caliber do you have and what power level/fps are you looking for. I can try to have everything preset for you.
Mike, please provide some details on your finished product, may a pic of the entire hammer and debouncer lying together or some sort of assembly sketch?