<font face="Times New Roman, serif"><font size="3">Depending where the arm is actually located (ability to get to it) :
1. (the better of the two solutions) - take a scrape piece of a servo arm and a flat tip screw driver. place the scrape piece of the arm onto the flat end of the screw driver and heat until the scrap piece starts to melt. Make sure it doesn't catch fire (if using an open flame which should be use as a last resort) and that it doesn't start turning colors (that is, getting burnt). With the z-bend still in the over-size hole, slide the screwdriver in (melted scrap piece up) and flip it over onto where the z-bend meets the over-size hole. Let is cool for a few seconds then move the servo. You might need to repeat until the hole is filled in.
2. Heat up a pair of needle nose pliers and just squeeze the hold smaller.

However if you have the spaceto get to it, I would agree withtacx and use a nylon clevis.</font></font>