I tried making a zero stop of sorts out of rings of black delrin for my 6-24x50 SIII scopes, something you can slip over the turret while you've got the knob cap off. I had problems getting the thickness/height of the ring right, though it shouldn't have been that hard to do. I think I was just not satisfied with the SIII's sfp and was looking for excuses to spend the money on a good ffp scope with zero stop. Wound up removing the SIIIs I had in service and replacing them with a 3.5-21x50 Bushnell & several Kahles K624i AMR scopes, and never looked back.
I went to Sightron's website a couple of weeks ago, and found that they're coming out with a new version of the SV that will have a zero stop - which was the last objection I had. If I hadn't already invested in the Kahles & several Athlon Cronus scopes, I'd certainly try one of the new SV scopes with zero stop.