[ChrisNZ]

Chris, the first time the right arm is straight is at "both arms straight" (after impact) and incidentally it remains straight into the Finish, with the left elbow bending (a sort of reversal of roles of the arms) for maximum extension into the Finish.

Weightshift, I agree. However it is the left arm checkrein which prevent straightening before "both arms straight". So what I'm wondering, is if you take the left arm off the grip, then is there value in rehaearsing the stroke with a straight right arm - rehaearsing it with a bent/bending right arm is not representative of what your right arm should be doing in the real stroke (striving to remain straight) - although it may give the geometrical 'look' of what is happening.

Chris