Down load some free plans for an Ugly Stick. 48" span for a 40 is good. Try the scratch building forum's sticky for free plans. Its as easy a build as you can get. I would stick with built up wings to keep it light.
Or down load Paul Swaney's 25 size TACO profile plan. an LA 40 should be close in weight to a ballbearing 25. also an easy build.