The Saito 180 IS a fuel hog if you fly it around full throttle. I doubt you'll be flying an aerobatic model around at full throttle all the time. So, thats not really a valid argument against the Saito 180 in this scenario. They will run fine on 5% or 10% nitro. You don't need the 30% that some guys run in it. They just do that because they need a little more power in a heavier bird.

I have no experience with the Magnum 180--so shouldn't comment.

I personally think gas is too heavy for a 25% plane. My rule of thumb is minimum 1000sq.in for a gas engine. But, guys are doing it more and more, so it's kind of that grey area where you could if you wanted too, but your going to pay the weight penalty for it.

Why not use a 2-stroke? They are cheaper and they put out more power than a 4-stroke. The old debate about 4-stroke torque will go on forever, but you already stated that your not flying 3D or unlimited performance. So, to me, it doesn't make sense to even consider a 4-stroke. 2-strokes are lighter, cheaper, and more powerfull. Not to mention ease of operation. 2-strokes either run or it's the fuel, carb, or plug. When 4-strokes don't run, you have to consider the cam, pushrods, valves, and rocker arms in addition to all the things mentioned about the 2-stroke.

Why not consider the OS 160FX, Moki 180, Moki 135, ST2300, Thunder Tiger 120 -- all 2-strokes. All reliable. All cheaper than a 4-stroke. All proven designs. Put the fuel tank on the CG and hook up a Cline regulator to any of those engines. You'll have a 2-stroke combination that can't be beat in terms of reliability, performance, and ease of operation.