I have never built a .12 Firefighter but I have built a .12 Firefighter Blazzin and will soon build a Firefighter gooycheese. I would suggest buying some Plans from http://firefighterboats.com/ , there is also some build instructions for the boat there. It almost sound like you want to design your own rigger, if so have you built a boat before? Will try and answer your questions if I can, the .12 boat I have is 3" outside tub by 22.15" tub length.