I found this video that discusses the shape and he also has a link to SVG and PDF files in the description so you do not have to design it yourself.    It sounds like he took similar spiral approach like Ross did.  I've queued the video to the point where he discusses how he fixed the release problem.   I have not tried it yet. 




--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.