Your RC mounts vibrate and flex like crazy Chris?........I have the same exact mounts for my 50" and to be honest i haven't felt any vibration what so ever.......and as far as flexing.....before I attached the 50" I checked to see how sturdy they were with my hand and they didn't budge....felt pretty solid........didn't you have a whistle noise from your 50"?.......There are fins on the back of my 50" and on each fin there are these clear plastic clips about an inch or so wide that slide left or right........2 sets one on the left and one on the right......I was told that you can adjust their position to dampen the vibration and tune out the whistle noise that some 50" make........I've tuned out the slight fin vibration whistle (didn't really bother me really) by adjusting the clips.......the RC mounts are cheap in price I'll give you that.....but they do the job quite well as far as I'm concerned......I'm sure somebody will be happy with them if you intend to sell them and the 50" in the future........
~Woodrow~