Along with my prior post:

I replaced the pads on the Dia Compes with Kool Stop Salmons - fit for older Campy shoes. When I took out the old pads, I could see that there is a cutout on the hidden surface of the pad to accommodate the anchor of the threaded rod. [see homemade diagram] The Kool Stops don't have this cutout, it's flush. This makes the pad bow out a bit when I put them in the shoes. Will this quickly wear flat against the rim, or am I creating stability/vibration problems by not having it sit flat in the shoe? Should I drill out a channel on the Kool-Stops?

Good point, and unknown what the result will be other than more rapid wear in center until it wears down even. Some (most) of the Koolstops I see on ebay have the cutout part, old weinmann's have a circular depression to allow for the bolt "head". Not sure how the center "bulging out" will affect brake pad squeal or toe-in either.....maybe scour some material out with a knife or other cutting instrument?