I added a HDPE (High Density Polyethelene) spreader plate to keep the stock handle from cracking the shell. It has worked so far. The concept was to spread the stress over a wider area of the shell and not concentrate the force between the two slots in the shell. This can be done with just a few hand tools.
Here is a link to the post I did about it, others also offered some other ideas:
http://www.rebreatherworld.com/semi-...forcement.html