Rikki, my experience is similar to yours including with SGM128. I think the only sure bet is to do the conversions as you suggest and combining the various drum channels (9, 10, etc.) to one channel (GM format- I think that is 10). What I find is that if you just use OMB with XGtoGM.con file there are some drum instruments missing (sYnerGi GS comparison vs GM).