James,
There are many la 46 set up topics in the past , around the southeast , 800 ft down to sea level , we use 10/22 powermaster or sig, 10/20. Half castor and half syn., .280 Venturi +/- .010 . With st NVA , 12/4 prop , apc , Bolly, or copy . 5 ounce capacity gets you in the ballpark with headroom to experiment
Many items affect fuel mileage to complete the pattern , more pitch requires more fuel, more nitro requires more fuel , more oil requires more fuel, bigger Venturi requires more fuel,
This is a very simplified information to give you a idea of where to start, plane weight, drag, engine mods , muffler , line size/ length, prop design, etc, etc All change fuel requirements