[bugsoup]

The castor shims are inserted between the bottom tube of the beam and the frame head. The longer bolts are so you have enough threads to hold the beam in place. You should only need them on the bottom.

I have Koni adjustables all around (from the TireRack), but I'm not sure how the weight of the wheels affects the suspension. I would guess that different shocks would help your situation, but I don't know what you should try. I'm sure someone else here can give you better advice on shock choice.