Too short is when the collar is not nipped up between the trigger guard and the rifle body. Too long and the fore-end isn't nipped up between the trigger guard and the body. Just right is when the front trigger guard screw nips up the collar AND the fore-end tightly between the trigger guard and the rifle body. I cannot think of a simpler way to explain it I'm afraid. The fact that it is a Mk2 fore-end makes no difference to the question. It's what is CORRECT is all that counts. Look..., stop fretting and getting into surmantics about trigger guard angles etc etc. The collar should be square at both ends and the trigger guard MUST BE FLAT and lay flat in its recess in the fore-end.

If you are REALLY concerned, forget the patch and just reinforce the section as per the L42