It's not as though those are the universe of options though, both of those options would be on my lower end for any hand made frame. The big issue would be whether you are making your own rack. If you have the option of moving up to 6mm bolt that would be highly recommended. There are also very solid areas other than the drops to mount larger fittings. Some of the expedition bikes use the tube drop junction where the socketed connection is essentially solid material.
If you have to stick with the standard parts then getting a billet drop would greatly improve strength over cast parts of essentially unknown quality. The brazed on barrels when placed in a partial circumference saddle have excellent strength (rear mount), probably more positive than the seat stay junction, so I wouldn't worry about them. keep in mind that the joint is mostly compression, and the barrel material is chromo, or possibly a better grade of bolt steel.
As far as brazing the rack directly to the frame, the main issue there is that it is normally done with fairly stout material, which means possible problems with 9mm pannier mounting hardware. But it also means that the rack is pretty stout. Any stout rack would be very strong even if it wasn't brazed/welded to the frame, and the frame mounting creates better options if the rack gets crashed or whatever and need replacement.
If you braze directly to the frame with lessor diameter tubing I think one runs the risk of a stress riser and having a joint fail. I'm sure there is a workaround, there is usually one for just about anything, but that would be my concern.
If my knees allowed me to do a world tour, I would consider 1/2" tubing in my rack with beefy barstock to barstock mounts and 6mm bolts, however I would also have holes for 5mm racks so that if the worst came to the worst I could slap on a cheapo rack over existing holes.
Last edited by NoReg; 12-14-07 at 05:02 PM.