Both bars are screwed into the 4 x 8 joist with gold colored wood screws about 2 1/2 inches in length. I have had two people on one bar before without any problem, so the mount and the bars are very strong. The bars flex a bit but it all holds together. William - your set up looks very strong with that center piece that holds the middle from above. Cool idea.
I'm going to re-do the set up I have a bit and leave that low bar in place for shorter people to do pullups but I am going to put another bar above the bar with the spinners (also equipped with taped spinners) with longer nipples so it sticks out a bit. The problem is that when you come down from the top bar to the bottom one it is way too easy to hit your fingers on the wall behind the bar as you try to get your grip.
More pictures when I do the update.
Easy stuff Keith. If I go east any time soon I will be sure to look you up. If you are serious about wanting some help with anything in particular let me know what you want done and I can help you think your way through it. The woodworking skills are really not all that difficult.