@dimpledweather
He would likely be better off buying one already modded and sell what he has imo.
Something with a popup piston in a pro saw near 60cc would be a much better tool up that high. Turning it super lean at say 5000ft would get it much closer before heading up to 10,000 or more. The saws I've sent out above 3000ft tuned super lean here at 50ft ran decent they said. The videos confirmed they were running plenty rich. I have some 034s that would be perfect for that or a 360 topend. The high compression will help the most. They can be made 200 psi pretty easy and parts are available new, AM and used.