had unexpected grief when I went to remove my PSRU from the engine.  reason was I was informed that the flex plate is to be held on the E shaft with a small circular squash plate to prevent cacking of the flex plate.  Since I had not done this I was removing the PSRU to put this plate in place. The PSRU only managed to come out about 1/8 of an inch and no further despite my encouraging for hours.  As I guessed the input shaft had rusted inside the E shaft despite my plane having never been outside in weather.  Finally managed to get it off by using my trusty tapered key puller, which is over 40 years old and has not been used for possibly 10 years.  Sure enough, there was slight rust, holding on better than any Loctite.  So rust polished off, and this time smothered in anti-seize all is back together.  Just to warn all that this could be an interesting problem if in rust prone areas.  You do not have to repeat my 2 day experience.  Neil.