I think I'd go along with "The Duke" on this. Nothing wrong with a little extra power. I'd say a 46 or a 52FS would be perfect for this model -- but it's flyable with a 40LA. It you ALREAY HAVE the 40LA go ahead and use it. If you are THINKING ABOUT BUYING model to use in this model, go for the slightly more powerful (and only slightly more expensive) larger engines.

BTW, I also agree that the SWII is a "draggy" design and to be perfectly honest that's part of why I chose it. I wanted a second-plane that would help me learn to fly the tremendously draggy WWI aircraft I like so much. My Fokker EIII has 16 rigging wires, a big open radial engine in a flat-faced cowl, a complex non-retracting undercarriage, a top pylon, exposed machine gun, and open cockpit with exposed pilot -- you can hardly get more drag than this! It most definitely does NOT glide well. BTW, my decision to leave off the cowl on my Spacewalker was at least partly motived by the wish to INCREASE the drag to better replicate the flying challenge of the many exposed engine WWI types.

So the SWII is an excellent model for certain purposes. I love the very realistic way if moves through the air. It looks real -- not like some models can flit around and perform moves that seem very unnatural. If this is what you want then you'll love your Spacewalker!