Need help with horn contact plate

[davidc22]

71 GMC C15 350/TH350. I am trying to get the horn to work as it didn't when I bought it. Horn circuit works, if I short the steering wheel nut to the plunger the horn sounds. I am using the original steering wheel. When I install the contact plate the outer edges sit on a plastic "ledge" which is preventing it from making metal to metal contact. I am baffled either there is some kind of metal plate missing from the wheel or the contact plate is too big or something else id wrong with the wheel [or I'm an idiot]. Everything seems right and I'm pretty sure i'm installing the contact plate correctly [like an upside down bowl]. Hope someone out there knows what I'm talking about and hopefully has a solution. I have bare metal at the bottom but the plate is sitting on the plastic lip [I scrapped it quite a bit and it appears to be solid plastic]. HELP...
I have searched and read but have not seen a similar issue.
Thanks