Funny I am finishing my stout arcas as well and I was contemplating the shear pins as well.
I got some 4/40 plastic screws from microfastener.com. I think that 2 will probably be good for this rocket. I also picked up some threaded brass inserts at lowes or home depot (forgot the size I'll check tomorrow). The 4/40 screws fit in nicely, so nicely in fact, a am trying to figure out how I am going to get the remains out of the insert. They push in but the screw threads catch on the metal threads on the insert. I think some CA on a toothpick might help. I'll let you know once I finish up the install and do some testing.
I will CA the holes in the paper airframe and that should be enough to keep the hole from enlarging.
If this doesn't work as expected I'll probably use some kind of metal "cutter" on the nose but the insert looks promising.
Awesome kit, isn't it? I am excited to wrap it up in the next few weeks and hopefully get my L2 before the end of the year. Only time will tell...you can't rush these things....
NAR 93283 L2 KB1YOD The opposite of success is not failure but apathy.