172 v 172 cup drivshafts

[Tommy 172]

I know these are different in length, my question is, is the extra length in the actual shaft itself or in the outer CV joint?

i.e, would i be able to fit a cup CV joint to the end of a normal 172 shaft and would it fit correctly?

 

[Gaverick]

I've got a ph2 cup o/s shaft in my ph2 ff and it works perfectly, slightly more torque steer but I don't mind that.