After field testing and tweaking my design, I've narrowed it down to one of two options. Each has its own perks. The first one shown is centered on the grip frame but requires more post processing after printing. The second one is offset but prints cleaner and requires less post processing. Update:
The project has undergone some minor changes since this original post. Here is a video of the completed model.
I've got my next project on the printer this evening. This 12-gram holder mounts to the frame using standard bottomline screws. The 12-grams are held in place via o-rings that wrap around the outsides of each end. Hopefully this will allow me to be less picky about o-rings should they ever need replaced.