“ ..... It is no use the part that the restraints are attached to moving in a different direction than the tub that is holding the person, and likewise seat attachment points also need to be considered like this. For belts the consideration must be for a six point belt not just a four (or less) point belt. ....” The primary function of a lap belt is to keep your buttocks in the seat during negative Gs. Lap belts should be worn low and tight across your pelvis bones. Shoulder straps help prevent you from head-butting the instrument panel. Air bags are a secondary method of preventing you from bed-butting the instrument panel. I prefer the newer air bags installed on lap belts of some Airbuses and the newest Cessnas. They inflate away from your waist, filling the space between your face and the panel. A fifth or sixth (crotch) strap prevents lap belts from rising above your pelvis .... and prevent you from “submerging” under the instrument panel. If you worry about rapid egress, install quick-disconnect door/canopy hinges that can be released from both inside and outside the cockpit. Apply military-style labels near outside handles to simplify the work of fire-fighters trying to drag you from the wreckage. As for r canopy-breakers ... crash axes are nice but require strong arms and room to swing them. An alternative is the one-handed glass-breakers carried by first-responders. My expertise is limited to sewing a few seat-belts (FAA TSO C-22) and repairing hundreds of parachute harnesses. I have survived one forced landing in a Beechcraft King Air, but hope not to repeat that miserable process. Finally, I have lost far too many skydiving friends and colleagues when jump planes crashed.