I have a set of possible Lyons wheel covers. They have no provisions to snap onto a wheel. They fit 15" wheels. They actually fit 56 pick up wheel really well except the center needs to be opened up so the hubcap will fit. The fit of the cap to the corresponding wheel area is perfect. I plan to cut them unless they fit a Cord or Caddy or something else expensive. They are NOS except one has some rust spots. I run 41 caps now but think Baby Moons would be nicer.
I like your plan and I think it will work fine.. I did the same thing on early Ford rims years ago and it worked well.. I'm liking the full hub cap look right now...