You don't want to exceed the charge rate, refered to C rating, that a lipo is designed to charge at. Since I've not seen the ratings ever listed anywhere... I'd suggest you don't use any charger with output that differs from the rapid charger itself.
You can certainly use the standard or the rapid charger for the standard battery with the extended battery. The charger works by sensing when the battery reaches a full 4.2v... So it doesn't matter what the MAH rating is for a particular battery...
