Ken,

I think I gotta disagree with you on something...

You said tri-stock on the engine side of the firewall wouldn't do any good. I think it'd actually be more effective.

Just to make sure we're talking the same language, I drew a quick picture, and included it. This picture is looking down from above on a typical tractor style engine airplane setup. The motor is pulling the aircraft toward the bottom of the picture. The yellow pieces are the tri-stock.

In this setup, the tri-stock is on the engine side of the firewall.

In this setup, the forces of energy would try to shear the glue joint. This is a stronger joint and harder to break. If the tri-stock were on the back of the firewall, the force would be trying to pull the joint apart, a tension joint. Tension or stretch joints aren't as strong as shear joints.