Capn' pretty right on there. Revell puts out a Typhoon kit that is 1/400 scale. comes out to be "17 by 2 1/2" and runs about $15-$30 online. So I imagine something 1/200 or bigger will run over $50. But that Revell kit I would think would be a good start. plenty of room inside for standard dynamic diving sub. Should help keep costs low as well. In fact, that is exactly what i am doing myself. and there will be room for a smaller WTC and ballast system down the road If I feel the need to go in that direction. But that size should fit 300-380 size motor and micro servos no problem. even non micro rx and ESC.