I think the internals are quite useless for concertrecordings. I've tried a couple of times but got better results with my selfmade panasonic caps wa61 mics. The internals are quite nice for lets say band rehearsals etc but for true concerts it's quite a pain.
Anyway, I'll give it a try. Above all, record manually using manual levelsettings, so adjust your levels on the fly. That means you'll have to check levels during the show and change when needed. You'll probably have to move the recorder in order to change recording levels which will be audible in your final result.
AGC OFF
LOW CUT OFF
MIC GAIN LOW
+T for trying though, fingers crossed!