G'day Rod,
Congrats on the impending purchase !!!
That's going to be one awesome scope. I didn't know much about the parracors until I was watching the Obsession Telescopes CD and it mentions scopes at f4.5 and that its highly recommended. That said, I then had the same thoughts as you, ie more glass, diminished views !!!
Back to the SDM, absolutely beautiful scopes. I think having it built locally could also add a bit of peace of mind should you need any support later on as opposed to getting an Obsession shipped from o/seas.
I'm really tempted to send him an email to see if he does 12.5" truss dobs.
Are you going for the extra options; Feathertouch, servo cat , Argonavis?