I don't think that frame misalignmment has anything to do with high speed shimmy. Many years ago a friend of mine and I were flying down Alexander Avenue, which is the route from the Golden Gate Bridge into Sausalito and he developed a "death wobble." He slammed on his rear brake and was able to keep the rubber side down. This was on a fairly new Ron Cooper, which came from Bicycle Odyssey, and I know that Tony Tom (owner, RIP) always checked frame alignment on high end frames before they were built up. Since we were in the neighborhood, we stopped to discuss this with Tony. He said he really didn't know what caused it.

As a mechanical engineer I learned about spring-mass-damper systems and how this can happen. The problem with solving this analytically is that there are too many unknowns, one of which is the physical attributes of the rider. The solution is probably just to change something to get away from the harmonic frequency of the system.

Things I've read that can cause this:

• Thin top tubes
• Low trail (although I did have a bike with high speed wobble which went away when I increased the rake in the fork)
• Weight distribution front to rear

There's probably more. Maybe frame alignment has something to do with it, but I've ridden plenty of mis-aligned frames that didn't shimmy. YMMV