Interesting Dave ..
I must say I haven't come across any cardboard spacers near the corrector holding ring ? ? seems a bit strange on a couple accounts, 1st, the corrector and ring should have already been manufactured to fit flush within the tube end recess, 2nd) I would be carefull doing up the retainer ring screws if its been 'propped' by some cardboard, may cause some undue uneven pressure to the corrector glass ? ?
In saying that, I have only had one C8, tho I doubt if the cardboard's would have originally come with the scope when new, seems rather unprofessional ? ?
Anyway, others may chime in and correct me if Im wrong
Another point of view about dust on mirrors, Personally, its not essential to have a mirror 'totally spotless' tho an SCT looks better if you cant detect any at 1st glance, either way, a few specs will definitely Not impede on performance - also, cleaning mirrors over and over is not good as even evry time you clean a mirror, even with the proper clothes and fluids, you will always be making very tiny micro scratches, hence, lightly clean surfaces
I personally consider that a few specs does not warrant another wiping session , but all to their own
It not totally critical, tho it is rather common knowledge that the fewer mirror cleanings the better
Sounds like you have done a good job all the same, tho, Id probably get a second opinion on those cardboard strips ?
But rest assured, I dont mind being wrong
Rgrds