Don't think they'll fit...
Hi Axel!
The -7/8 wing is slightly longer, thus one or both of these items has to be different. But, I do think the flaps and ailerons for a -6 will work. You use to could buy these in QB (read already built) form from Van's. Had a friend who bought a flap like this to replace a twisted one. Not sure if they are still available, but might be worth checking! Also, lots of -6 parts out there!!
Good luck!