I use HP5+ in 220 with my Mamiya 645 all the time and have never had any problems with fogging. I can't imagine why the type of film would make any difference. 220 works fine.(posted 8801 days ago)As a side note, I sometimes feel that 220 with the Mamiya 645 and C- 220 is sharper than 120. Maybe its just me, but I think the paper backing might have something to do with it.
have fun on your trip.
chuck k