Similar to how you can shorten or remove the spring spacer, except w/ a shorter spring the spring rate is greater. Just a little different is all. Pretty cool tho ay? Mine uses the full length spring w/ the spacer removed and it shoots ~9ftlbs. Super easy to cock (12lbs), smooth shooting and quieter. You can also replace the spacer w/ more spring. The spacer is 1.5" so enough spring that at coil bind = 1.5" (~12 coils of .122 wire) which will lower the spring rate but net you more avg spring force thru the stroke for more power. Would be cool if they made springs that long but I haven't seen any.
The only fyi for removing the spacer competely is the sear can catch the spring when fired and bend the spring. So you have to improvise, like making a plastic shield to block the sear from the spring but allow the piston to pass during cocking, like a sheath. Or mod the sear so it won't catch.
I mention the above b/c I know you like to experiment.