Best to do, is putting the implement in lowest position, slide out the ends of the pto shaft, and put the couplers on both plined shaft ends. When you hold them next to each other, you can see how much play it has when the shafts are slid into each other.
Once i bent a 100 Euro PTO shaft with endpiece, when i took a aharp corner with a too long PTO shaft... the endpiece moved eccentrical in turning circle of about an inch... It made my drum mower shake over the field, and with a manure tanker, the wheel bolts of a front wheel ran loose because of these vibrations... /forums/images/graemlins/confused.gif