I made a fin alignment jig for the LOC IV (and some other sizes). It worked but for it to work like I intended it needs some modifications (longer tube section for the fin tabs and the hole for the motor tube needs to be a thru hole.
Center hole slides over the motor tube, Fins slip into the slots. Fat end fits into the sustainer. Obviously the rear bulkhead isn't installed (just the middle and front). I twisted the fat end to make the vertical fin vertical and the other two lined up. Tack with super glue, dry, add epoxy. I also used my guillotine fin jig on a flat surface and a framing square to visually align the top fin to the vertical.