Interested in Good, Lightweight Clampshere, I filed the inside of the leading edges of the clamp shoe, those that parallel the back edge of the clamp. This prevented the shoe from biting on the back of the alluminium bar as is common with alluminium clamps and also allowed the shoe to move freely. Waxing with furniture wax made the whole thing as slick as can be. More on the second clamp shortly. These clamps cost £8.99 – £12.99 inc tax depending on length. Here is the link for the 2 footers.