Yeah, looks like that's the way to go. Seems like pumpers are the answer for big bore 4-strokes. I once put a Dellorto pumper on an ATK605 and the difference was like night and day. I was able to tune the pilot circuit better because the pump took care of the off idle stumble. My guess is that it's pretty much the same for the big XR.
I sent an email using the address on Barnums page, but it was sent back. I'll just have to give them a call.