Just a nit, askaref.com is not Jim Allen and is not official USSF policy. Jim Allen's site is: http://www.drix.net/jim/ While I find that askaref.com is VERY worth reading and they are, at most times, right on the mark, it is not official. Jim Allen's site is, at least for US refs.
Sorry about the link. Jim's site is called "Ask a Referee" - "a" not "the" - and I've got it bookmarked so I didn't check the url.
Gents...I suggest you watch the video entitled "The Grey Areas" which has a very nice piece on impeading...as does the "Myths of the Game" We use both for instruction here in NJ USSF Ref....hope you have this figured out should you come back to do games at PDA!
I got it all figured out now... with all the changing interpertations, we're bound to miss one from time to time... I'm looking forward to the PDA showcase around Thanksgiving. I also will be out around early spring on a weekend or two to pick up some of the early league games and I'm hoping the Girl's memorial day tournament.