i hear you...
i tried sanding the bottom of the draft box, but i didnt get the result i wanted. your rubber band idea sounds like it could work. apparently the stickers that protect the seat stay are supposed to help raise the draft box and increase clearance. however, i didnt find them to do much of anything.
in the end, its probably easier to run a 22 on rear wheel.
Toro Performance
i tried sanding the bottom of the draft box, but i didnt get the result i wanted. your rubber band idea sounds like it could work. apparently the stickers that protect the seat stay are supposed to help raise the draft box and increase clearance. however, i didnt find them to do much of anything.
in the end, its probably easier to run a 22 on rear wheel.
Toro Performance