Thanks for the tip, Limey. I use wire brushes in my RTX and drill motors all the time, but it may never have occurred to me to stick one in the drill press. Having two free hands sure makes manipulating fasteners easier.
Last weekend I had a chance to work on the panniers. I initially envisioned mounting them on a beer rack like I did with the CL, but those racks are kind of heavy and I don't like that they use the fender as a structural element, especially on the XL; the CL's fender has a nice curve to its cross-section, so it's fairly stiff, but the XL's fender is more broad and flat and mine's already dinged up enough from bouncing it into trees and stuff as a kid. I can imagine it folding easily under the weight of a rack and panniers. Probably just as bad, it's only held on by three dinky 6mm screws and two plastic sockets. I'm going to avoid placing a load on it.
Unfortunately, the upper shock mounts are the only two obvious tie-in points on the XL frame. I should probably just weld a couple tabs onto the back of the hoop, but since I'm a crap welder I chickened out and fabbed up a bracket that avoids modifying the frame.
The bracket slides over the back of the hoop, then the two bolts deform the flat bar up top, pinching it around the tube. It's solid, if a little funky.
Next I cut rails that run from the shock mount to the bracket out of the same 1/8" x 1" bar and fitted up the panniers. It may be a trick of the lens, but at least in photos they look surprisingly proportional on this bike, given their dimensions. I'm a bit shocked but I'm glad I stuck with the fat fifties.
Having the drill press makes this so much easier. I've been cruising CL for the past few weeks in search of a 14" vertical band saw and a belt sander to round out the basement workshop, but so far no deals have turned up. As it stands I'm cutting all the flat bar and channel with a hack saw. What a pain in the ass.
Now the plan is to add a stay from the bottom inside rear corner of each pannier to the bottom taillight-bracket mounting bolts on the fender. Hopefully this will be sufficient to stiffen the boxes up laterally. Vertically, the rails are good to go, but I could also weld a piece of bar flat along the top edge (so, like angle), which would help side-to-side rigidity. I'll try making the stays out of fender washers welded to 1/4" rod and see how it goes.
As you may notice in that last photo, spring has sprung around here and other projects are aggressively jockeying for my attention. Hopefully I can get back to the panniers soon.