Drilling tiny bits of sprue for clamps on my KT2 was driving me mad, then I had an absolute brainwave. Went to the garage and got out my fishing tackle, dug out a box of Pole float caps (For you stateside guys - small hollow rubber tubes to keep tiny floats attached to fishing line) The box in the first pic contains several hundred and is about £2 or $3. They vary in ID and OD, the ones on the extreme left perfectly fitting a 0.4mm wire that goes in the tiny holes in the Aber clamps.
Because they are rubber thay can be trimmed after gluing to reduce the height, without any danger of breaking off the clamp. The last pic shows a finished Barrel cleaning clamp with trimmed rubber