For those who are mounting electronic view finders (EVF) with mini ball heads or perhaps variable friction (magic) arms, you might have run into the issue where the EVF can spin loose as you apply pressure against the eye cup or may be too much for a hot shoe to handle. Ball Heads and Friction Arms work pretty well, but they aren't the best way to mount an LCD EVF monitor.
Here's another EVF Mount that's recently become available. This one mounts to a set of 15mm rails preventing your EVF from spinning loose, and can be quickly adjusted in various angles through the slotted brackets. Starts at $115 + shipping via eBay (found here).
15mm Dual Rail Clamp Adjustable EVF Mount