[hharney]

Pressurized G model POH states:

The airplane is certified in the normal category. The normal category is applicable to airplanes intended for non-aerobatic operations. These include any maneuvers incidental to normal flight, stalls (except whip stalls) and turns in which the angle of bank is not more than 60 degrees. In connection with the foregoing, the following maximum certificated gross weight and flight load factors apply:

Gross Weight:
T/O Wgt ........................................4700 lbs.
Landing ........................................4465 lbs.

Flight Load Factor:
*Flaps up ......................................+3.8 -1.52
*Flaps down ..................................+2.0
*The design load factors are 150% if the above, and in all cases, the structure meets or exceeds design loads

Maneuvering Speed .......................155 MPH
*The maximum speed at which you may use abrupt control travel.

Never Exceed ................................230 MPH
Maximum Structural Cruising Speed .190 MPH

Most modifications will not adjust the operating limitations. Way too much expense involved. Although the extended fuel cells increase gross weight (normally not for landing but take off and cruise) the operating limitations remain as published by Cessna.

By speculation of the events, one would conclude that the pilot exceeded the operating limitations but don't rule out that there was some kind of damage or deterioration that was already present and the timing was not on their side.