Just sorted out oars from Collars (great place to visit, thanks Bob).
Max length you can get in a Mk2 is 7’11” I thought initially that you could store longer by laying on the floor and sticking the end in the forward storage area but the problem is that the thwart gets in the way.
Collars only make 8’4″ nowadays for some reason but will happily cut to size there and then for you at no cost.