I have a LOT of F-clamps so many I don't know how many exactly. I have a habit of buying a few every time I at the mall. Can't have enough clamps because I build boats. The thing is especially with these cheap MIC F-clamps is that the pad of the screw is easily destroyed by constant use. I've been meaning to replace the pads on many of my clamps but all the approaches I'd come up with just did not sit well I suppose. Just now I came across something that I think will really work for me:

I'll loose some capacity but that's ok.

It is not really clear in the photo but I would put a washer on that pad. Following this train of thought, a wood pad could also be placed on the fixed end of the clamp. I would attach it with silicone so it can adjust to a workpiece but not fall off.