RE: OS 46AX OR 55AX FOR A SIG ?????????
Both the .46 and .55 AX are excellent and will power your SSE well. Personally, I would go with the .46 for a couple reasons. The first is prop clearance. The SSE has pretty short squatty gear. You'd want to change this with the .55 to avoid breaking props excessively since it seems to like larger ones than the .46. Second is flying style of the plane. This is just my opinion but I think the SSE is really fun with a high RPM engine. I flew mine with a Super Tigre .45 & Macs muffler. The thing screamed and flying was fun. Again, that's just my personal preference based on what I like. Other engines, including 4-strokes will fly the SSE great too. Some people even prefer them.
Whatever you choose, you will like. I own 2 .46-AX's, one .55-AX and I just got a .75-AX. They are by far the best all around engines that I have owned.