Yamaha DTXpress/DTXplorer/DTXtreme

Hi,
 
I've recently got a Pearl Export kit, fitted it with mesh heads, bought  some 
ddrum red hot triggers, mic cables, etc and set it all up using my  dtxpress 
sound module (original).
 
The idea was to get something that looked, felt and played like an  acoustic 
kit ... and I think (hope?) I'm almost there (as I've added the RHH  hats on 
my normal hihat stand as well). Cymbals next!
 
It all works but the triggering is a little inconsistent. I do  occassionally 
get a missed trigger on the snare (e.g. reasonably fast press  roll) and the 
bass repeat triggers sometimes.
 
Can anyone help with the settings I should change to rectify the  problems?
 
Really appreciate any help.
 
Ta,
 
Tom