So it turned out that Tandy Printer Adapter v2.0 was only compatible with the EX / HX machines and not the Big-box SX/TX/TL machines as they have a heavily recessed Edge connector.
So I designed Tandy Printer Adapter v3.0 for those machines and it works great!
The only issue with it is I designed it before I got a case for my OPL2LPT, and while it fits, it places too much strain on the two connectors for my liking - I think it could be solved by grinding down the section of case causing the issue.
Other than that, it does work perfectly. :cool:
PS, for those wondering, I placed all the connectors on the front of the PCB as I thought some folks may wish to mount it on the back of their cases with thick double sided tape.
PSS, this adapter is also
not compatible with the 1000/A/HD - they use different pinouts and requires different wiring.