Ok so my 60” Sharp has the 400x400 pattern and I currently have it mounted on the wall with this mount. Seems to be fine. I also realized that the weight I said in my original question was with the stand, it is actually 59 lbs with no stand. The mount pattern and weight works with this mount, so it seems that the extra 2.5” on each side don’t really matter.
Also, to help the guy above; this mount says it goes up to 55” TVs, not 50”.