44.3mm sounds pretty generous I only intend to use a 183 camera so it'll be interesting to see how the imaging circle works out, but it should be OK by the sound of it.
I've just got to convince the knurled ring around my secondary to unscrew...
I have the same exact setup, C6, Hyperstar v3, and ASI183mc pro. Keep in mind the back focus calculation starts at the base of the threads, not the end.
This post I believe shows a C6: https://www.cloudyni...hyperstar-bits/
Setting the Hyperstar for "zero tilt" is really helpful too. The picture shows a pretty good description on how to set the zero tilt. I think I used dimes or pennies instead of nickels since they are thinner. (Sorry, I do not know the currency in AU )
I also ended up buying a ZWO T2 tilter adapter because you will soon discover that tilt you could get away with on a normal scope is just not sufficient at F/2 (if you want to do serious imaging), even with a smaller sensor like a 183. Critical focus is literally measured in microns.