The diameter is around 1.7mm...not many drill bits are that size. Plus, the roll pin compresses to fit and keeps the key fit snug when inserted, preventing it from wobbling back and forth.
Numerous people have successful used this exact one (mine is in the mail). You can program yourself if you have 2 stock keys.
NEW GT STYLE FLIP KEY REMOTE FOR 2011-14 FORD MUSTANG CLICKER CHIP KEYLESS ENTRY | eBay