RE: Magnum 4 stroke
On to the Mag .80 4-stroke. I have the Mag .91 and my buddy has the .80. I also have 2 Saito .91s. The Mag .91 and the Saitos are about the same in power. The .80 is a little less, but a nice running engine. Both need to be broken for a gallon, anyway, as do the Saitos. Give them 2 or 3 gallons and you'll see what I mean about breaking in.
I see the .80 is "Sold Out," so that may be the end of them, but they were what I would consider a best buy for sport flying. Maybe they'll be back.
As I said, I have 2 Saito .91s and a .72 and a Mag .91 & .70 and my buddy has the .80 and a .52, as well as the 2 .30s and we can't fault the Magnum 4-strokes for anything. All ringed 4-strokes are going to need an extended break-in compared to an ABC type, but that's what you get with a ringed engine. Do it right and the compression will come up like you wouldn't believe. They are copies of the OS so it's hard to fault the design. They aren't polished as much, but when they are broken in, they run as well. And they are a good bit less expensive.