I haven't tried the EFK system...however I am using the Wolff Gun Springs two piece non-captive dual 21 LB spring system in my Glock 29 with very good results. It has worked very well with both 10mm factory and aftermarket barrels, as well as the 40S&W, 357Sig and 9x25Dillon conversions. Wolff Gun Springs does offer different spring rates to suit your needs. I have the calibration pack which contains Extra Power.........: 19, 21 & 23 Lb springs to dial in perfomance to my needs. The 23 LB does make racking the slide more of a chore and in a defensive situation this could be an issue for tap and rack, etc.
Check them out http://www.gunsprings.com/index.cfm?...ms&cID=1&mID=5