The piston mount attaches the piston to the main package tube (MPT).  The piston screws into the center of the mount. 

CAD:

FEA:

The piston mount is fixed at the outer holes, and all other forces act on the center hole. 

Piston Actuation:

Piston actuation applies 425 lbf to the center hole, FOS of bulk: 5, FOS of bolt: 3.872 and the drogue drag force applies 80lb, for a FOS of 7.8.

Main Deployment:

Main deployment applies 457lb of force, FOS of bulk: 2; FOS of bolt: 3.872

Material: Al 6061, ⅜”