I have noticed that the rig geometry of the Mk IV is very similar to my Mk 1 woody across the beam. These are the settings that I use:-
My boat is a Mk 1 Porters woody and I use Pinnell & Bax sails, measurements taken with the rig under tension of 350 pounds, standard Selden mast etc.
940mm across shrouds at spreaders. Spreader length 515mm (shortest distance). Spreader deflection 205mm. giving a prebend of 42mm at the spreaders. I sail with the mast raked at 23′ 5″ when we expect to be overpowered and at 23′ 7″ for light winds.
These settings are fast upwind for medium and strong winds. Very light winds are another story as I and/or my settings are slow.
The fore and aft geometry or the measurement point for rake is obviouslt different for the Mk IV