doesn't sound right that any manufacturer would make the wheel pad so thick that it couldn't be run on standard studs.. it's a safety issue. i'm still leaning toward that the mechanic's assessment is off..

did you have aftermarket wheels before? did you have hubcentric rings already on there and forgot to take them off? check to see if the wheel bad is actually against teh face of the rotor..

if worse comes to worse.. here's the extended studs i use
http://optauto.com/index.htm?stocknumber=ARP1007711