What is the threading of the holes tapped in the trailing arm to secure the hub? I can't recall if it's 1/4-20 or 1/4-28. I want to put in Heli-coils, but I don't want to get the wrong bits. TIA, -- Phil Barnes (peb3 at cornell.edu) Keeneyville, PA '71 TR6 CC61193L (31 year owner)