So my 7 year old has discovered Batman and comes to me this morning at breakfast, telling me it would be cool if he had a flying "Batwing"...
John,
You are pleasing a 7 year old. Something approximate will do. Remember the old akronym, "KISMIF..Keep It Simple Make It Fun".
Get yourself some COROPLAST from an old discarded sign at a local store, enlarge and use the outline you have (or draw it on the coroplast). After cutting the outline, seal the edges with masking tape. Cut a wedge-shaped hinge line on the bottom, leaving the skin at the top as a hinge...work the line a few times to loosen it up. Apply an engine and controls installation like the "Platter" as mentioned above. This can be found on the Aeromaniacs web site. Paint with dope or rustoleum. Voila!
You could also use balsa, it would be lighter, but you would have to piece it together with good use of grain direction, plus make sure you use "C" grain to avoid warps.
Good luck. I'm sure the fun time with the old man would outweigh any accuracy issues.
George