I had this camera with the AE-III prism and speed grip, and I am considering to get it again. I like to photograph quite fast and found this easy when doing horizontal shots. But not when shooting vertical, never being quite sure to hold the camera with my right hand on top, or left hand on top.
Anyone had the same difficulty? Perhaps you have some advise . . . maybe I missed out on something. . .
However you are comfortable. With a prism and speed grip... oh I also use a focusing lever.... I hold the grip with my right hand n finger on the fire button, the left hand is at the bottom (the camera's bottom not the turned bottom) for a nice sturdy hold and focus using pointer n middle fingers.
I'm right handed and right eye dominant and my ETRSi is fitted with the Winder EI 2, so I hold it with my right hand on top, holding the winder grip, finger on winder shutter button. Left hand underneath to focus and add some support. This makes it easy to put my dominant right eye to the prism finder.
If you are left eye dominant, you might find another position more comfortable and stable.
Without a grip and prism, it's a real pain in the ass.