Magnetic Wheelchair Activity Tray Mount

I designed this a couple months ago so my daughter could have an activity tray that attached easily to her wheelchair arms. It uses a dozen 60 x 10 x 3 mm Neodymium bar magnets and a 12" x 16" food service tray. We don't use it a lot at home, but her PT at school says it works great and she gets a lot of use out of it.