Dead easy..........cut off the standard threaded section ( about 30mm long )............set up the hub / carrier in the drill press and drill straight thru.
Will need to do a smaller pilot drill say about 6 mm followed by 1/2 inch drill.
Metal is pretty hard........good drills....and cutting
oil !!
( I/2 inch is also the correct size for AVO spherical bearings ......not 12mm like most are using)
I turned the spacers from 30mm 4140 bar
Wide base of spacer ensures that up / down and shear forces imposed by the coil-over unit are largely converted to tension along the bolt axis.
Result is a single shear connection with a lot less offest......distributed across a wide spacer, rather than a bending action with the original set-up.
Also improves coil-over location a little. Win Win
Muz