Not sure if the idea ever took off. Brandon at Mull is pretty good at responding to PM's. Shoot him a message.
Personally, I'd reccomend just getting the trans cut next time the motor is serviced.
Are you happy with the type of power the T5's deliver? Or do you want more top end charge? A stock stroke cub will certainly deliver that. Although the cub cylinders are really gonna shine with different pipes. Yeah sure you see guys with Cubs and T5's a lot..... But that doesn't mean it's an adequate set up. If you do a cub, take the time to wait and make sure you can do the entire package right. Just slapping a different set of cylinders in there isn't gonna make it worth your while.
To boot, Driveline is producing stellar results on a fairly new platform. The Athena's have been out for some time yet run pathetic if the junk nikasil even lives. They need tons of work to even get them to run decent.
Better port lay out, symmetrical ports, available in higher and lower port timings, top notch nikasil from Millenium, and Driveline is able to port them to suit your needs. They also sell quality domes for your choice of fuel.