You're all wrong! The Spitfire has a high aspect rig. Here's another
pictu

http://wingsail.neuralfuzz.com/wingsaildesigns.htm

By having two sails the center of effort is kept low, but the efficiency
of the sails stays high.

Thom Stewart wrote:
Crapton,

You're blowing smoke. Spitfire doesn't give a damn about slow speed
sailing. It is interested in the very upper end of sailing speed.

That is the reason for the choice of "Low Aspect" sails. Larger sail
area with less heeling moment. Burying a Foil to heeling would kill
speed faster than "Air Vortex"
They increased SAIL AREA without increasing Heeling Force by adding a
SECOND SAIL without increasing HEELING FORCE.

Two sails: Increasing driving force of the wind without increasing the
Winds leverage for heeling. This increase of the second sail, off to the
side rather than a Ketch Rig, made the Multi Hull necessary. This had
the advantage of adding Hydrofoils at a wider angle. Increasing speed is
made possible by sailing flat, using LOW ASPECT SAILS without the need
to carry a Heavy Weighted Keel to overcome the Heeling Force created by
a TALL MAST carrying HIGH ASPECT SAIL (Sail with a larger curve)

That, my friend, ends my attempt to ENLIGHTEN you. Open your mind and
learn

Lesson over, filleting complete.

Ole Thom