Hi Terry. I saw your tweet about the Dick Smith colour board. I never saw such a thing.
I have the TRS-80 Hardware Manual. Do you have a copy? I guess it might be worth figuring out where this board would connect to.
As an aside I have a lower case TRS-80
The character generator is capable of lower case. You need to solder on an 8th RAM chip though as a piggyback on one of the existing chips. The address line is one of the legs bent outwards and soldered on by a short wire.