A:Answer VESA 300x200
Research your mount and don't assume "up to 400x400" or 200x200 / 300x300 will support 300x200. I bought a Kanto : VESA sizes (mm x mm; W x H): 100x100, 200x200, 300x300, 400x400, and incorrectly thought that 300x200 would fall in somewhere. It did not. Luckily, the mounts tech support arranged for an adapter to be sent out to me, and it worked out. 300x200 VESA pattern is a rectangle, some would say it is still standard, but I wouldn't agree with that. Look at some mounts and see if you can find 300x200 specifically. For me the mount had to be heavy duty, full motion, and within the budget. I ended up buying a Kanto PS300 (heavy duty! Great!!) only to find out that it did not support 300x200, but Kanto tech support took care of me and got me an adapter (Arrowmounts AM-201D) shipped (THANK YOU ! :)