Applaud you Allan for your perseverance in nutting this out finally
Been following your adventures with this 10" f4 Newt astrograph that you're building with great interest.
Noticed that originally you did try to use a 40mm extension (to lift up your mirror) and now after your last foray it seems to need a 49mm extension lift; well you must have a patience of a monk (don't know whether these days there are any patient ones left!
) - good on'ya to be able to resolve it to your satisfaction and looking forward to more images after this
HTH
Cheers
Bill