I use the SJC and the Carbon Arms Gas Hog. The SJC works very well but it's heavy, loud and has a pretty good concussion wave or whatever with it.
Gas Hog works the same is much lighter, quieter and less shock wave. I vote GH.
I run a 20" LW Criterion. I got it because with my 17" handguard and my hand at the end of it (6' 5") I got a nasty powder burn from the SJC comp on the 18" barrel. I went 20" with a sweet Gas Hog comp. Problem solved but it's not a problem a lot of people have.
That Stretch 16 looks like a winner barring special circumstances like mine above.
I recently found on sale at Midway extended chokes for the FNH SLP shotgun. They were cheaper than both Briley and Carlson chokes. They have a blue ring out on the end.
FYI there will be a little gap between the choke and the barrel. Are you screwing it in with the choke wrench? With lube? Take a picture of it in the gun. All mine say INV for invector
What extensions do you use? Taylor's fit no problem. All fit with varying degrees of pressure. Meaning a good smack and they fit.
I wasn't having that. I have the proper burr(cutting tool) for the soft metal, I used my dremel as I thought my air grinder might be harder to control. It went well but as I said a lot of metal removed. If you want pics pm me you email.
I will add I think there is quite a range of tolerances accepted at Glock so each case is a bit different.