OK, sorry for the delay. I'm not a machinist and not sure these numbers are correct but this is what I came up with:
Hole Dia = .234 / 15/64"
Metal stock thickness = 0.02"
I'm also going to try asking someone with an actual adapter if they'd be willing to take measurements also.
Thanks for your help and interest -
Dick
edit: 15/64 (not 15/16) geez