The paint should be good on a wheel stop. The only time a bumper or wheel stop is ever used is in the case of an accident or mistake. The train crew should bring the car to a stop and set the brakes before the car touches the bumper or stop. Mark, I've never seen a wheel stop installed between a siding and a switch, but that doesn't mean that they are never used that way. All of the wheel stops or bumpers that I have seen are installed at the end of a stub siding. I think I have an old issue of a Railroad Model Craftsman somewhere or it may be a Model Railroader that has an article with pics of various bumper designs and wheel stops used by the railroads. If I remember correctly, there were pictures of dirt piles at the end of the tracks, stacks of ties at the end of the tracks, wheel stops, and various designs of bumpers. The bumpers included everything from rail bent up and braced with more rail and welded, to concrete. It seems that if a railroad had something that would work laying around when they needed to install a bumper, they would use it.