[Mart]

If it helps at all I modified some nuts for this application. I took some 10mm flanged nuts and ran a 7/16 UNF tap through. I might have turned the flange down a little too. These 10mm flange nuts use a 15 mm hex, which is 1mm smaller than even the reduced hex on the 5/8" hex nuts. They worked well and a 15mm socket fitted well in the space available.15mm is approx 19/32"