In order to make a 9 speed MTB rear derailleur to work with an 11-36 tooth 10 speed cassette, I had to put in a longer B-tension screw (pretty much dead center in the image). I used an M4-16mm screw and it seems to be long enough to do the trick, moving the RD jockey wheel enough to just clear the 36 tooth cog.   (8/16)