If the mixture is set right, it will use approximately 1.5 ounces per minute at full throttle, so I'll let you figure what size you might want from there. Keep in mind though, that with these big gas engines they are rarely flown at full throttle all the time. A 16 ounce tank works fine in most installations with this size engine. That would theoretically give you a 10 minute flight at full throttle, or a really long flight just putting around....

AV8TOR