Sounds like a book I've seen... Moto Columbia, about the RX3 transversing Columbia... I'm sure the mountains of Columbia are very similar to those in Peru.
https://store.cscmotorcycles.com/Mot...p/csc-1999.htm
If you search the backlog of the CSC blog Joe Berk talked much about his South America adventure on an RX3 and how it managed loaded with gear but I don't think they did two at any point though.