I am trying to put a rear rack on my boyfriend's Jamis Durango. There are really handy and convenient braze-ons at the tops of the seat stays to attach the racks.... but there is nothing to attach the rack to down near the drop outs.

I considered p-clamps, but the tubes are shaped in such a way that the p-clamp wouldn't really clamp on very well (not to mention the disc brake is in the way on the other side).

Ideas?

Consider a seat post mounted beam rack instead.
or you might fare better fitting panniers on the front instead.

fork .. rigid or suspension?

The bike has front suspension. Also, the rack is going to need to handle some serious weight, so I don't want to go with the seat post option.

How about tapping a bolt hole in the flat part on the seat stay near the drop out? I'd have to look at it, but I would be surprised if the bolt size (M5?) that is typical for rear dropout eyelets would affect strength there at all.

There are a few ways of going. One is to use a Delta Disc Rack (look under the megarack button) like this one.



It mounts mid-seatstay but it isn't very good for panniers because of the single leg. It will mount at a more normal height, however. You could do the same with the MegaRack but it would stand a bit higher on the bike. Below is the Megarack on a bike without eyelets.



The other, more expensive option, is Old Man Mountain. It replaces the quick release skewer.