The Gunter rig is an almost forgotten rig. This is a pity, because this rig has many merits.
The Gunter rig is as good to windward as any sloop rig. The rig is very efficient. Even more than some triangle mainsails. Because the upper part of the Gunter rig produces a lot more force than a normal mainsail. When you look at the latest development of main sails with a batten in the upper part, which resembles a gaff rig, everybody understands what I mean.
The Gunter rig is more flexible and forgiving than a normal rig.
The mast is relatively short. When the boat is on the trailer, the mast is not longer than the boat itself.
The short length of the mast makes setting and lowering the mast a lot more easy and safe.
Many "experts" proclaim that a full batten rig is not possible on a Gunter main. This is not true as can be seen on the picture above. The Sonderklasse was founded 1899. The picture shows one of the last boats sailing on the Kieler Foerte. As is it clear it works also for big boats. The picture was made last year.
We have taken it a bit further and use a system in which the gaff slides complete up or down the mast, with a provision to unhook the gaff on the upper slider, so it can be turned back. This is necessary for sail setting and adding the battens. The gaff is set with one halyard only.
The drawings and the description is an excerpt from the KD 650 design for which the rig was designed. The sail area of the rig is 18,6 m2. The strength of the rig is sufficient till 22 m2 for an catamaran, 24 m2 for a trimaran or proa and 28 m2 for a slender mono hull.
You are free to scale up, but this is to your own risk.