ok i understand the misunderstanding. I am using this old measuring tape with funny units - dunno what they are - and these aren't inches - DAMN!!!! - sorry dude - my bad. - god i'm embarrassed! -

THESE ARE THE CORRECT DIMENSIONS!!!!! 370mm main tub length, 70mm width at its widest point and tapers to a point 15mm without the 2mm walls on each side of the transom so really 19mm - my bad again - at the rear. This is kinda compensated for by the relative height at the rear (30mm).

470mm front tip of sponsons to rear end of tub. 540mm tip of sponsons to rear tip of rudder - overall length.

you can't really compare my rigger to yours as the booms are right up at the nose of the tub, and not further back as they are in yours. i do have a 380m 3800kV which i'm tempted to use.
Sorry for the mix up - i'm a right goof sometimes.

Andrew