"I looked at the Tapco website(thanks for the update vbrtrmn) and found that their double hook trigger group is not supposed to fit in an S12. With a little work, it does but I DO NOT RECOMMEND IT!!!"
I stand corrected, here is the actual wording from the Tapco website FAQ page.....
"Will the TAPCO double hook trigger groups fit in a Saiga .223?"
"No."
I'm emailing Tapco about the S12 now.
Mikel