Good ideas!
I need to fashion a set for my Dodge 2500.
Overload leaf is at the bottom of the stack.
Stable loads for this truck require drilling the overload leaf to mount them (and apparently that sucks so bad they give you 4 drill bits with the kit!).
I have some high durometer rubber froma bridge girder bearing pad. Either that or slice 2 hockey pucks diagonally and mount in there.
Think if I can carve out a notch in the rubber that is parallel with the spring I could get away with hose clamping them to the spring itself.