I use mostly a w799 frontwing on my m8 fusalage, but bought for more wind a older W720 balz pro with smaller m6 bolt holes. Is it possible to drill the 3 holes in the 720 front wing from the current 6.5 to 8.5 mm so i can use the same standard m8 mounting bolts on both front wings?
We do not recommend this type of operation on the following wings:
W679
W720-BP
Source: sabfoil.com/en/help-center/faqs
I wonder if a thread reducer on the fuselage would work?
Helicoil will work as a reducer
The problem with such a thing as helicoil is that it is pretty much permanent. Once you have converted the M8 to M6 with it, it will be M6 forever. If you ever want to use a M8 wing again, getting the helicoil back out will be difficult. Otherwise, use those cone washers with M6 bolts for your M8 wings.
Helicoil actually uses a slightly different tap and thread.
I'd consider I stalling a thread reducer on the bolts themselves with some thread lock. I also wouldn't leave it assembled and accept that those bolts might have to be cut off in the future.