Great to see you and Pete putting some effort into this beast Robin. It's always fascintated me every time I've looked at it (wistfully). It SHOULD be capable of some devasting pics on paper.
Really hope you get it singing. Then, for goodness sake, don't bump it!
You really do need to be using the Catseye gear, especially the autocollimator. I expect a mm either way on primary or secondary would be enough to knock it out at F/3.8
I wish Skywatcher or an Australian version of Orion UK would put out an F4-5ish 12" Newt with struts (CDKish?) to keep weight right down. Big secondary and 3" chinese corrector. Then again I also wish I had a cold beer and it was sunny right now.