The plastic guide-rod it really isn't that much of a difference, not even a 1/2 oz. I have one, and do install it at matches that will weigh the gun, but only as an additional precaution to avoid a DQ.
What really helped is that I lightened the back sides of my grips to save weight.
here are 2 different setups I use, both are under weight. I use the 18 round mags, with the 17 round mag base pads.