Also see Storer's solar boat: http://www.storerboatplans.com/Solarboat/solarboat.html
A couple thoughts: Lillistone estimates 10 kts, not 10 mph, and also estimates lower HP to drive it at that speed, so you wouldn't need to run the...
Lillistone designed a boat that approaches the initial specs: http://baysidewoodenboats.com.au/designs/three-brothers/