Ok, the plan to use ndm/pacer couplings on the dev coach was a non starter. They were too long by about 5mm to give a consistent distance with the other cars. Here’s the dev coach to ndm compared with the tgf…..

So the tgf couplings received a 2.5mm hole drilled as close to the blade end as possible

and then shaped to approximate the ends. Here’s an untouched one and one I’ve attacked next to it. A lot shorter

Fitted to the bogie, gap much more acceptable