The two pictures of the guy holding the Pentax 67 in the West End Camera Club blog post should not be seen as the correct way of holding this large camera. The lens must be cradled during the actual shooting handheld, and as a long-time professional user, I cannot agree that having two grips on the camera improves anything in the actual shooting practice, other than a bit of cosmetic improvement (but it's a working camera, not a dolly).
When the P67 is tripod-mounted, the use of MLU is standard procedure prior to tripping the shutter. This technique will guarantee beautifully sharp images while hand-holding will very potentially introduce blur from shutter/mirror inertia (and we are talking about quite a large shutter and mirror!). The early Pentax 6x7 (1969) was not as well dampened in the shutter area as the later Pentax 67 (1989).