I've got an 04 GL1 with the PREMIUM soft ride FE2 suspension. I would like to get a larger front and rear swaybar, perhaps from an FE3 equipped 'Ho or GAGT.

I know the FE3 front is larger - what about the rear?

The FE3 front bar is not larger; it is a solid 24mm instead of the FE2 hollow bar. All rear bars are identical from the factory, to you must go aftermarket so find something stiffer.