Use zip ties to hold the rack in place on the seat stays as my rb doesn't have braze-ons there. It has bolt threads for the lower part for fenders, I think. But I used them to hold the rack legs in place. Put some blue Threadlock on the bolts and all seems well. I wound some electrical tape around the seat stays and used a couple of black zip-ties. The medium 8 inch ones. I carry a couple exrta in my seat bag in case one snaps, but I've been doing this for years and haven't had one break, yet. Sometimes I'm carrying as much as 30 lbs of gear, too.
Just mounted some Christmas lights I got last year from Target, so now I've got zip ties all over the place as I wrapped my frame w/t lights. I just wish they had a set that blinked, too.
