Hi Mark
have you thought of the Model Slipway "Wyeforce" (twin screw)good to build and brilliant on the water, my wife loves it and I can go sailing 7 days a week if I want too ,now that she has her "Wyeforce !!
I’m now building the "Aziz" (twin screw) and thats going well, so perhaps you could put these in to the think tank as well
Checkout http://www.modelslipway.com in their gallery album for my boats and their reveiws on the "Aziz"
Peter