Pete,
Thanks for the reminder - - I would have forgotten to drill them.
Ed,
Your point is well taken. The entire swingarm has to twist in order for that to happen. But there is only so much that can be done to stiffen up a long swing arm. The rear axle passes thru holes in the internal solid blocks of 3/4" aluminum which makes what are called "moment" connections. This ensures that one side cannot twist without twisting the other side (as long as the connections are tight). If you look at older swing arms, usually round, they terminate in flat plates that have less resistance to twisting than the rectangular tubing with the internal solid pieces, especially if they are not extremely tight. The only way I know of checking this is to physically grab the rear wheel, top and bottom and try to twist it. On this design, when I try this even with the front end tied down, the whole bike frame twists simultaneously, so I feel that it is very good. Luckily, I'm not planning to run any more slalom courses at Bonneville, at least not intentionally!
Tom