Chad yes your backplate should have arrived as noted in the listing with a 1/4 hole and stepped for easy drilling to 5/16 or whatever.

If that has not occured then the solution for you that would be the best is to access your fellow club member and request a spare adapter ring set. OK look at this link for another spinner I am not suggesting this spinner but pointing out what you need and ii is that set of plastic insert adapters. These acompany many brand of spinners just not what you bought. I think you will find your fellow club members will have accumulated these by the thousands and it would be no problem.

http://www3.towerhobbies.com/cgi-bin...&I=LXE155&P=ML


John