Now that I've looked at the GSX manual, I see that this situation is indeed addressed.
I made the edit for KRMZ, set it's visibility to 0.3, and now GSX uses KMRY BGL for KMRY gate areas - so all is well now. I tried 0.4, but evidently KMRY gates are within a 0.4 mile radius of KMRZ, so 0.4 didn't work.
Thanks for helping me.
Steven Miller