Yamaha DTXpress/DTXplorer/DTXtreme

i just put a pintech CC101 mesh snare on my dtxpress and i put the 
selfreject on 0 (like i did with my kick to get all the notes) but 
what relationship should the reject setting have to that and what does 
it even mean/do?  if i do a flam, the second hit isn't triggered?  and 
in the middle of the pintech head, there is this foam column that 
obstructs any natural sound or feel that I can't even figure the 
purpose for.  can i take it out?  it seems glued in there.  edrums and 
great but they are not simple.  any suggestions anyone (especially the 
man in the know, my boy Ed)?
rock and roll everyone (if that's your thing)!
Frank