This thread certainly old but helpful. I tried machine screws as noted by stratigunds but was able to pull them out when tightening. The original parts are on crazy forever back order. So, I went for it. I ran a 6m x 1.0 tap through the upper two mount holes. I put in some 6m x 1.0 bolts with spacers and was able to tighten without pulling out. TV been up all weekend.

Note that your results could vary. I was prepared to drill out and install a thread insert if this trick failed. Certainly a bit of risk involved.