With that little air, he'll probably just have to wait till you get there before doing any jetting.
I'd get a couple sizes smaller mainjets to take with, and a smaller pilot jet.
My experience has been that the pilot goes down one, mainjet down one (or two), and sometimes the needle drops a position also.
Of course, we've had two of the same bikes (XR 250's) at 8,000' and they both took different jetting (completely stock bikes, same year). This is why I say wait till you get there.
We can throw rocks at it, and get it close, but fine tuning is pretty essential up that high. Don't forget spark plugs! Even with re-jetting a few of our bikes fouled plugs last time we were up that high.
BTW, lower octane gas is better at elevations that high. You probably already knew that!