One can make as many wings as one wants, but all the wings must point to the dot. Now there is a mass center and wing-lines. After that you must join the wings. When you have the boomerang shape ready you have to imaginate the mass center is the boomerang. Don't finish until you are happy.
Paper is cheap, cheaper than plywood.
This is not so exact, but if the blade has angle of 30 degrees or more from vertical, it might be possible that your model is not working properly.