Most discussions of using a prism with a Rolleiflex are bsed on the 90 degree model. This places the camera full in front of oyur face and changes the ergonomics significantly more than the 45 degree prism, making something like the pistol grip very helpful for many people.
The 45 degree prism is actually very close to using the camera with a WLF, having it up close to look through the magnifier. No need for a pistol grip- it handles very smoothly, your hand will fall in the places you know from regular WLF use, etc.
Yes, the Hassleblad/Kiev prism makes it top heavy. Nothing extreme, and the strap points are high enough that the camera still hangs in its usual fashion around the neck.
For those of us without F models or other Roleis with interchangeable viewfinders, I am not sure what can be done short of something like my complete breakdown and construction. What I have shown is not interchangeable in the field for a WLF or such.