I have taken plenty of shots with the 45mm lens and a Vivitar 283 of the artwork around my academy. However, only a few of those in the panoramic format. The Vivitar flash has no problems covering the wider scene, at least not that I noticed.
I just put the shutter speed to 125 and fire away.
By the way, I often use the XPan in normal format. That way I can get mounted slides and view then with a regular projector. Of course, when the occasion arises, I shoot the panoramic format, which can be very rewarding.
Anyway, It's just such a nice camera to use that I prefer to just use it in either format, rather than trying to hunt for that panoramic shot...
Below three images taken with the 45mm lens, Vivitar 483 flash, and Fuji 200 Reala film. Sorry they are so big, but I had no patience to resize