George:
I bought a mount from Costco. When test fitting it, I found it would be the height I needed and would allow the TV to swing away far enough to get other things in the cabinet, if I mounted it up high on the ~1.5" thick right side of the cabinet. the bolt holes were high enough that the lower ones took a big lag screw and were just above the bottom of the adjacent cabinet. the top ones protruded into the cabinet a bit, but cover nicely. No extra post required.
the Costco unit will support up to a 47", so plenty strong enough for the little TV that just covers the trim at both sides. The TV has to move slightly to the left to get the cabinet door open.