[PeterM]

Simon,
Rule 1 Check with Don at Bintel.
Rule 2 Check with Don at Bintel.
Rule 3 Check with Don at Bintel.
You get the picture.
Mine is also an R model but I have never taken the corrector out, the Rs are about 5 years new so there is no chance any spacing shims would have rotted.
As I can see with a torch there is a dark grey looking foam along the edge but I can't see any spacing shims because of this. My previous Classic model definitely had them as I did take the corrector out several times. Doing a quick Google and looking up the R model shims on Cloudy Nights finds some references to them in this model. Some time ago Don explained the importance of putting these back in the same place.
And BEFORE you try to take apart the 2ndry I would also bring this up with Don, the R and ACF as I understand it have had major changes to what is in Kens images above. Just be very careful, talk to Don first as he does this almost every other week.
Infact going back over your initial post I have been exactly where you are after installing Bobs Knobs. Follow Tony's advice in post 13 above then you need a defocussed star that's not too bright. Start the collimation process with say a 20-25mm eyepiece and then make very very small adjustments to a knob then recentering the star using your hand control set to the very smallest movement. Then doing another very small adjustment and so on until you start to see an improvement. Once you get to this stage use a higher powered eyepiece and go over the whole process, again very very small turns and recenter using the Autostar. I would be doing this before attempting to pull things apart again.
Peter