Okay, so the rack arrived today. I set it up on the bike, but found that the smallest cog of the rear cassette is so close to the braze-on that you can't get a long screw all the way through it and through a nut without it running into the chain when it's in 7th gear. The rack came with shorter screws and the thread of the screw matches the thread inside the braze-on, so I put some locktite on it and screwed it together. Is there some kind of spacer or something that would allow me to get a whole screw plus nut in there, or should I just not worry about it?
It feels pretty sturdy and has three supports on each side, but we'll see what kind of a load it can carry.