Sam,
What I and probably a lot of other people are wondering is why were attempting to fly a 675 mm sector low level and VFR in an aircraft certified to 25,000 ft. when the conditions were marginal VMC? You were stacking the odds against yourself surely. You can quote CRM/cockpit gradient as much as you like but CRM does assume the participants have a degree of basic airmanship.
I have done that sector dozens of times in singles. It requires a great deal of detailed planning and beyond all an acceptance to wait around until conditions are correct.
it is sad that as PIC your passenger was killed. I am surprised the licensing authorities did not have more to say