This is a huge picture, so I'll link it. Please let me know if it doesn't work.
It looks like they may be made only for use with triggers with built in stops, but I can't confirm that. I've sent this picture off to STI to ask their opinion.
What's going on is, after install, the trigger overtravels and allows the disconnector bar to engage the sear and would cause doubling and hammer follow.
The problem is fixed on my pistol, but I had to round file a relief in the disconnector to do it. Shouldn't have had to do this, and wouldn't have, except that I plan to get a C&S kit when finances allow.