The way those pentax camera are constructed are made for eye level use. Just like the mamiya rangefinder I'm after

I tried having a look on the net to find a picture of a person using a prism on a mamiya rz67 or a blad or similar where they are usually used at waist level.

It looks like you would have to 'cup' it from beneath with both hands like you are going to drink water from your hands and raise it to your eye....