I have attached a big Wald basket to a bike with Nitto swept-back style bars before, and recall that the bars I used had to be shimmed to use with the existing (26.0) stem that I used, so I am baffled that the Wald clamp wouldn't fit the smallish 25.4. I wish I could see how you've got the clamp configured. As regards scratching, if the bar is beautiful, I will wrap the bars two or three times with cloth handlebar tape before clamping.