But time for some updates. After a couple days rest I attached the rest of the knobs onto the thrower and tackled the pop mech. It arrived Monday, our post put it in regular instead of expedited when I came into Canada, but there would have been no way I would have had enough time to get it installed.
RJ has great instructions on how to install so I won't rehash that but here is what I did on the inside using his springs rather than the elastics.
I got 2 of the springs from RJ and this one is attached to the bolt that is holding on the rear cylinder and then attached to a lock nut on the arm. You can see the old extra hole where the guide rod used to be on the original version.
The second spring is attached to the bolt that is used with the latch and then I was able to slip the other end on the 4-40 inside the barrel. That was a pain to get on. What I did was use a precision flat head screw driver and slide the other end of the spring over it, rest the screw driver on the end of the bolt, and using a small allen wrench, push the spring down the driver and onto the bolt. It took a few tries but it worked in the end.
I took Phil's idea of adding in some foam where the bolt slams into the thrower body because it is pretty forceful. I had some scraps from my neck foam and cut a small piece for that. It helps cushion the blow quite well.
Now I just need to figure out how to get the thrower lights to work with this.