RE: New twin design project
Goose:
The SWAG rule of thumb concerns all side area, it doesn’t matter if the area is a float, a nacelle, or the main fuselage.
You need to remember the lateral area is the complete fuselage, TWO nacelles, and TWO floats. It’s not just the projected area that you see in a side view.
I still think it would be best to lengthen the afterbody, the fins will be out of proportion when they are big enough as short coupled as your plane is.
Lengthening it shouldn’t be hard, you are planking the fuselage so the longerons you’re having cut can be scrapped – balsa will be strong enough to hold the more widely spaced formers as you do the planking. And with a gentler curve you’ll find it a lot easier to plank, too.
Bill.