Nice indeed. I especially appreciate your patterning of it. You'll be well prepared for Louis' Shotgun 1 course with what you've done. I too would run slugs through it in advance of the course to make sure you have them under control. My 870 likes both the Federal LE low recoil slugs and Brenneke's home defense slugs, also low recoil. There's almost nothing that my 870 doesn't like, though, except to be left at home and out of the game.
For what it's worth, mine has a factory two-round extension now and used to have a Wilson two-round extension. It has been around the block quite often with both of them but never had a problem. What I found early, though, is that plastic followers tend to degrade in time and have caused me some problems. Switching to a metal follower solved them all. I use Hans Vang's in my 870 but other brands work well too. Cheap insurance, I think.
Enjoy yours. The 870 is a good friend that thrives on familiarity, I think.
