So I guess now everyone with 400 posts can say they've added their 2 0.2 cents.
Edit. I was off by a factor of 10. You need 4000 posts to claim you've added your 2 cents. Guess I still have some posts left!
Basically the higher N-number you see the stronger the magnet is. The highest available so far is N52, but I've never seen those on sale. It's not hard to find N48 (second strongest) on ebay however.
I think that in the case of doopydoo it's cast together with the receiver, and thus not movable. I think that a separate bold would be a cool addition to any kit. Might be able to get some cool cocking action.