I recall reading somewhere about using a Gas Gas swinging arm in the TY mono back in the day. Am I making it up or was it related to another bike?

I think mr birkett did it for the ssdt and it snapped through the week .

It's the swinging arm off an air cooled gas gas, it has to be modified though to fit. And yes Birketts snapped in the ssdt

Thanks. Won’t bother with that idea if Mr Birkett couldn’t make it last. Although it wouldn’t be exposed SSDT conditions, I don’t have access to the same m/c engineering skills he has.