I just read the thread and it made me think. When you are making any changes to a Newtonian e.g. new focuser, it becomes much like a ATM project. You must consider what changes a modification may make to the optical axis. There is a program avaliable from the net called "Newt" which will give you some idea of what will happen when things are changed (follow the link).
http://home.att.net/~dale.keller/atm...t/newtsoft.htm
I can not comment on the GS Crayford, but I would assume that it either has a lower profile then the original R&P or that it does not have enough travel, additional if the scope was an f6 there may not be a problem with "draw tube travel". Maybe the point here is to consider the "draw tube travel" when selecting a new focuser Skywatcher 8" f5.
If the "brass compression ring" is similar to the JMI then all is required to secure the eyepiece is a gentle tweak of the screw, the eyepeice should not move. As GS is Taiwanese the manufactoring tolerances may not be as good as JMI so it maybe slightly large the 2" hence it pushed the eyepiece or collimation tools in the opposite direction. A probelm that can be fix but at additional cost.
Just my thoughts on the subject
Anthony