Thanks for that info, but I don't think I'll order again from that source, as the product is not well designed at all. It turns out, I think, that it might be made for the RC after all, but the extenders are held to the paddles by four very little set screws that push into the thin edge of the paddles. This works for a while if you only push on the original area of the paddle, but when you press on the extended portion, top or bottom, the torque quickly flips the extender right off of the paddle. Maybe the double sided tape will help. I may try that, but I'm thinking the solution is a little shaped piece between the set screw and the edge of the paddle to spread the grabbing power of the set screw over a bigger area.
This little part has turned into quite the project, most of which should have been done by the designer or the seller.