This may help, here’s how VRC HS shafts are generally coupled, since there is no legal coupler:

It’s pretty simple, just 2 shaft collars sandwiching a metal 12 tooth gear.
This may help, here’s how VRC HS shafts are generally coupled, since there is no legal coupler:

It’s pretty simple, just 2 shaft collars sandwiching a metal 12 tooth gear.