Welcome aboard!!! Grew up fishing Erie and Ontario. Until I saw that you moded the mold I was going to ask if you used the Stand Up Spin Jig mold, the crane swivel is put in and you pour it up.
Are you using live bait or plastics on the heads you're attaching the rattles to?? for rattles where we tied them we painted the heads, put a piece of shrink wrap tubing with the rattle inside and sealed it up. For plastics I used to have the little rattle core cutter tool, then slipped the rattle into the hole and melted a little of the plastic on top to seal it in.