Tim, have you checked out DIY Drones? there are plenty of different ideas on there regarding hulls. I agree with Paul and go cheap and then transfer all your gear to a better hull later.
Here is an option. http://www.horizonhobby.com/1-5-scale-float-set-han6030 Ditch the upper supports and you have a 1m long cat.
I have gone down the Carbon Fibre path with my hull. I run twin T200’s with vector mounts for steering. I get about 45deg either side of centre and my boat turns on its own length. With a commercial grade sounder, dual beam transducer, GNSS Receiver and batteries, my boat is running around with 20kg of equipment on it. With all that weight, the boat runs nicely at just over 4kph. The system is 12V so that normally runs at 14Amps which gives me over 4hrs runtime. My boat is 1200mm x 600mm in size and is very stable. Are you wanting a platform just to muck around with navigation or do you want to do sounding/mapping?
