You can lock down the rear wheel with the adjusting nut, no extra fat folk needed.
A plastic wedge from the chain saw department will work to "jam" the chain and sprocket. Instead of putting it between the chain and bottom of the front sprocket try going between the chain and top of the rear sprocket. No chance of bending the shift shaft there.
A plastic wedge from the chain saw department will work to "jam" the chain and sprocket. Instead of putting it between the chain and bottom of the front sprocket try going between the chain and top of the rear sprocket. No chance of bending the shift shaft there.