Yes, the motor is placed as far back as possible to get the CG right.
You could use rigid 5 mm shaft coupling, and a 5 mm steel or titanium shaft of suitable length.
Of course, near the propeller you need a 5mm ballbearing to support the shaft. You will need an aluminum bearing support, I made a two piece version on my chinese lathe...
When considering a titanium shaft, check the diameter very carefully!
The weight came out at 59,3 ounces, with a 4S 3200 mah battery. So, your model will generally somewhat bigger than my Triala.
Regards,
Wolfgang