I have had good results using a 20# ISMI spring on a solid steel, captured guide rod in both Glock 23 and 32. The steel rod adds a bit less than an oz. at the muzzle. I believe keeping the muzzle down helps to reduce "limp wrist" failures by keeping more of the recoil impulse straight back rather than rotating the muzzle up. The heavier spring also gives a more positive return to battery and changes the recoil profile slightly.
I have tried and do not recommend round wire springs in the Glock. There are advantages to flat wire recoil springs.
Edited to add: This combo can make slide velocity higher on the return to battery. Std Glock mags may not lift the rounds fast enough especially if the rounds are a bit weak (less slide travel). I use Wolff +10% mag springs in all of my Glocks. I have kept some of these mags loaded since 1995 and after the initial break in set, I have measured no further shortening of the springs.
If you want to save your mag springs and make them more reliable, load the mags that will be kept loaded -1 rd. At the range it doesn't make a difference.
