A few years ago I did some experimenting with FX-2 and TFX-2. I have a particular fondness for the rich midrange tones glycin is capable of and I liked these developers for that reason. I did find that grain was more pronounced that I liked with 35mm, although obviously it was not an issue with 4x5.(posted 8199 days ago)It's been awhile since I looked at the formula for FX-2, but it seems to me the ratio of glycin to metol is more like 10:1, not 1:1 as in your formula. My suspicion is your developer is not utilizing the glycin much at all because the metol is doing all the work and therefore providing nearly all the density. My guess is your formula should perform about like D-23, or with NaCl added, like Microdol-x. Another thing, FX-2 uses potassium carbonate as the activator. In your formula, SS is doing that job. That works okay with metol, producing a fairly soft working developer, but glycin needs more of a kick. So even if you add more glycin to your formula, I don't think the pH will be high enough to activate glycin.
I don't have the formula for FX-2 handy, but if you can't find it elsewhere, email me and I'll get it for you. You also might want to pick up Steven Anchell's excellent Film Developing Cookbook, which lists many formulas (including FX-2) along with a trove of interesting and useful information you would be hardpressed to find elsewhere. Also, check out Ed Buffaloe's tips on developers at his site, unblinkingeye.com.