YES ! ! ! !

I'd forgotten about the diesel option. And I even used to fly diesel combat!!!! DOH!!!

Even running at a high rev and power setting I'd get over 6 minutes on about 2oz of fuel. And I understand you can get much more time per oz by using an engine that is designed more for sport flying. The fuel can be a pain to find though.

Not sure where to find the spark conversions. I know you can find them for some of the older 2 stroke loop scavenged OS engines as they were approved for SAM competitions.

I have an older 40 Surpass and run it for 10 minutes at a time on 4 oz of fuel and land with lots of reserve. Not much power but it's miserly. Fits in with the NON overlapped 4 stroke design. Probably a good option if you want or need to stick with glow fuel.

The old timer model is a good starting point. It wouldn't be as good as a purpose built design but you'd have something to fly afterwards that has character. The Bombshell is quite a lumberyard so its going to be heavier. Go for one with a basic stip built fuselage to save a little weight. One of those old Texaco models would be terrific. Or that Lanzo model with the wire cabane mounted wing would be a killer design. Big box of a fuselage and a HUGE wing. The 40 Surpass would be just enough power to lift the model and a couple of quarts of fuel. Or run the gas option and one of the repo spark engines. A Super Cyke would be nice but the front bearing might give problems as it's so short. Find a sparky that has a decent length front bearing and you're set.

But either way if you want to build an old timer design and don't plan on entering SAM events with it then you can always change the wing section to something better. Some of the new high lift stuff from Selig won't work as you need composites to build the super thin trailing edges accuratley but there's lots of high camber "balsa friendly" sectoins you can use that are better than the Grant's and stuff that many old timers came with.

For the record I've got a Roger Hammer Flamingo that I fly using an older OS 35 loop scavenged engine. 84 inch span and a super wide center chord with something over 1000 sq inches. 5 1/2 lbs and it climbs like a homesick angel getting to 500 or so feet in about 90 seconds when proped for a climb. For an even like this I'd probably try using a 25 and see it it could carry 2 quarts of fuel.

Speaking of fuel feeding, you'll probably need a holding tank set up with a float valve with the tank mounted higher than the engine and holding tank. There's no way the engine will suck 2 quarts evenly from full to empty of course. Maynard Hill did this in one of the record accounts from the 70's. A one gallon high mounted gas tank running to a float shutoff equipped 2 oz engine run tank. If you can't use gravity you'd need a fuel pump. And more batteries of course. Also he make his own tank equipped with numerous baffles to prevent the fuel sloshing around. You can imagine what a quart of fuel in a 2 quart tank will do to model trim if it's slapping around from front to rear. I know I wouldn't want to be the pilot.....

Starts to make the purpose built model look better, doesn't it. In any event I think it's safe to say the engine and it's fuel per minute is as important as the model. I hope this is a team event for planning and building as well as flying.