For better tracking and control I'd recommend a DK rudder. Just contact Don Kiesling by email: This email address is being protected from spambots. You need JavaScript enabled to view it. and explain your needs. 9 inch surf rudder should do it. He needs accurate measurement of rudder shaft length to top of machined shape / square.
As an aside, if you ever get a chance to trial a Fenn Spark you might just love it at 73kg. It will sit down at a better waterline than your mako and the bucket will actually fit so you get the discovery of contact and control with your hips. The secondary stability is very good.
CrabStick, Perth Western Australia
Current Boats: Epic V9 ultra, Fenn Swordfish S, Fenn Spark S
Previous: Think Eze, Stellar SR, Carbonology Boost LV, Fenn BlueFin S