Not building a 12 but couldn't you use a countersunk screw/tinnerman instead to give clearance?
Carlos in Arizona
EAA Chapter 538 President, www.538.eaachapter.org
Wittman Tailwind W8 N53CH (built & sold)
Pazmany PL-1 N2029 (bought & sold)
RV7 - N537TC (reserved & building)
Emp, Wings & Fuse done - working on FWF
"The air is an extremely dangerous, jealous and exacting mistress. Once under the spell most lovers are faithful to the end, which is not always old age." - Winston Churchill