I like working on older bikes and I see these all-the-time without really understanding them. My primary question; that I致e wondered about for awhile; is: How do you know when the rear wheel is absolutely straight. It seems that the eyeball method could never be really accurate, unless by chance; and that even a minuscule error would cause extra tire wear, at the least. What is your method to set the adjusters, and is really important?
The secondary question I have I guessed with no proof. I can see how the ability to adjust the wheelbase would be a nice feature. Lengthen it when you need extra stability, control, and comfort; shorten it on race day.