one more thing you can add is a taylor freelance seattle slug....a 3 oz brass slug (they make a black one too) that fits in the backstrap channel....this isn't a simple cosmetic plug, but fills most of the backstrap with weight, slightly reducing felt recoil....the only downside is that the last time i checked, they only make them for the compact and full size glocks...nothing for the subcompacts....
it also helps balance the gun out while shooting as we know glocks become increasingly top heavy the closer you get to emptying your mag....i install one in every new glock i buy....
http://www.taylorfreelance.com/seattle_slug.htm