17 and 16 wheel combination

[Kmamac]

Curious if this fine beast is anyone on this forum? It was photographed by a friend of mine at a track day.
It appears to have a 16 inch wheel at the front but a 17 conversion at the rear. I’m curious how this works. Maybe a great combination given the 16 inch front and steering angle allows for a shorter wheelbase than usual for the L twin BUT you have a big choice of rear wheels. I’m kind of asking as I do have a pair of 17 inch wheels I was planning to use on the sport but this option is only half the aggravation ! My mate reckoned the swinging arm was all changed but having looked at the bike this afternoon I reckon a 17 will fit anyway.