This is a different take on the remarkably effective and simple Quick Connect Shim (http://www.thingiverse.com/thing:22851). I found my shim would fall out from time to time, so I made this one which has multiple thicknesses, and (I think) clips on slightly better. It's also easier to remove, and slightly harder to lose ;-)
This takes about 2 minutes to print, and doesn't need any special settings.