I just bought a Mark V. I love it so far. Seems to ride quite well. The Mark V has a higher bottom bracket than the Jamie Roy. The bottom bracket drop on the Mark V is 5 cm while on the Jamie Roy it is 7 cm. Therefore, it is easier to grind a pedal on the Jamie Roy. Top tube is longer on the Jamie Roy, wheelbase longer, & it also has a less steep head tube angle.

The frame on my Mark V seems to be very stiff, but it has a comfortable ride. Not a light weight (which I didn't want), it weighs 22 lbs as Tony set it up for me with the standard wheels, a freewheel & a fixed cog, front & rear brakes, & Nitto steel track bars.