sirwalter..thanks for the info
From the first pic you posted, it looked to be a 'v' hull, but it is really a flat bottom. Being a little sneaky there aren't you ?
The dimensions you show are as close to perfect as you can get for that size motor. Of all the 1/2A hulls I've built over the years (at least a dozen), I stuck with a length of around 18". Some were shorter, like yours, and they all performed well with little if any difference.
Your's should do very well the size it is...
btw.........these small hulls are perfect for using a monokote finish.