Does any one have a good way of attaching an arm to a basic wiper motor like you would get on monster guts? I need a longer arm than the ones provided. I've tried attaching metal bars that I have drilled a hole in. Then I will use washers and a nut and hope to get enough compression to hold the arm in place without it slipping. That doesn't always cut it though. I see videos all the time of different props using these motors but nothing about attaching the arm. Thanks!