Thanks for reaching out to us, Steve, and for the detailed photos. I think the 15-213 is definitely the better choice. However our dimensions are a little different and I can't make yours out, precisely. Double check your thickness dimensions (both your shoe and the 15-213 are skinnier at the top) to confirm whether or not this will fit in your window track. If it does, then I think it's the one to go with.
I'm afraid that we don't have a shoe in this style at 1/2" thick. The 15-213 is the closest we have at 9/16", which is 1/16" too thick. I am sorry that we can't offer a better match.
The brake isn't meant to pad out the thickness of the pivot shoe like that. It's meant to lock the shoe in the track to prevent it from moving up and down so that you can safely remove the sash. If your shoe is skinnier than ours, then extending the brake won't really do anything, since that would also be too skinny to perform its function.
I couldn't find any version of this shoe with only a 1/2" thickness, unfortunately. I'm not sure who else may have that size.
