I tapped the deconpression hole on one of my puch 65 metras and it had been overbored twice. The hole actually looked closer to the bore. Make sure to get that tap strait and keep it lubed. I threaded in a set screw with high temp rtv in the threads, then I covered the top of the screw with a little more RTV sealant just to make sure it sealed off tight.
I havn't had any problems yet. Actually, I solved the air leak I had because the bore was so close to the hole.