BF tires will fit on any standard buggy rim, this combo is usually called BF lights or Moonlights, they'll fit the rear, but the front forks will have
to go to clear the bigger rubber. I'm not sure if KiteTrike offers bigger forks, could always get some made.
Best bet though if you're going with BF's is a bigger buggy all together, the Libra ones while costing a little more can take the big tires and
bouncing around no problem, they also make it really easy to handle the larger amount of power needed to pull a bug through the soft stuff. I'd
seriously consider getting either a new, or if $$$ prevents, a used libra buggy, getting the proper BF forks and drop downtube then make your own BF
lights and slap them on.
Plus side, the Libra stuff really doesn't depreciate that much, so even after beating it for 3-4 years, you can polish it up, throw on a new seat and
bearings and still get a decent dollar for it.
Sysmic S1 Buggy.
0.7m / 1.4m / 2.0m PKD Buster I
4.4m PKD Buster
10m JoJo RM+
6m Flysurfer Outlaw
12m Ozone Access