I like your approach to the +1, +2 extensions. I use Pearce extensions on full frame Glocks with no spring mods at all - the longer base plate balances the volume of the added round (1 in 45, 2 in 40 and 3 in 9mm - making a 20 +1 G17/34 - not a great carry weapon but a nice HD option. ) - how do your +1, +2 shoot? If they pass the acid test I'd say short of a patent you have a very nice personal improvement for a carry 40 S&W round!!