Looking at the rules of the competition, the airframe and engine should be the easiest part of the equation. Defining your avionics to meet the competition requirements looks pretty hard! Glow fuel is cheapest and most flexible option, especially if you can keep it in the 90 or less size four stroke. I can easily fly a 90 fourstroke at 1/2 throttle for 20 minutes with a 14 oz tank. For a total mission time of 40 minutes, depending on the distance, a 20-25 oz tank should be plenty. You need to design your navigation and surveillance system first, determine the final weight of that system, and then you can define your airlift needs. Keep your wing loading between 17-24 ozs/square foot, and you'll have a nice slow, stable flyer that won't get blown around to easily by the cross winds.

Brad