Steve, I would drill it out for a 3/8" roll pin and use a solid pin it it in stead of a spring steel roll pin. The spindle will handle the bigger hole with no issues.
That's good advice. The roll pin's just didn't seem to work. If you use a bolt, generally the shank is slightly larger diameter than the threads--you make sure the shank extends within about 1/8" of the opposite side. The fine thread allows greater leverage when tightening it down--grade 8 of course is much stronger than a Gr 5 or GR 3. You could also drill it slightly under the nominal size... say 23/64" and fit the bolt to it. One other thing I did with my CCs was to "knurl" the vertical part of the axle shaft with a center punch.
Thanks for the input.