Hi Deane,
As far as I know, the moment you use a mirror mode in gmax/3D modeling tool of choice, it will also mirror the bump map. Only way around that if really needing a mirrored version of the texture is to make it in the texture making process and adding it to the texture, and therefore also add in a corrected bump effect in the normal map creation.
Complicated, stupid, I agree, but that is the way to do it as far as I know.
I did some mirrored stuff my self, on some roof, messed up my normal map effect a little, but figured, not to bother with it, was not that easy to spot and till this day, no-one has complained to me so...
As others say above, it actually looks great with the mirrored effect, but sure, for some other stuff it might not look to good, so it is a good thing to figure out how to best make it, like I see you are trying to do.
And, yes, I agree, I would have though the program would be able to also mirror the normal map, but, sadly, it don't look like it can, darn, one day in the future maybe such help will happen in our 3D creation programs.
Keep up the good work, and I am happy you got lot of good advice from others about the mesh library setup.
Best wishes
Linda