Haha,
Yes, the arrow you point to is a horizontal piece of 2x4 that is at the "angle" of the monitor....those two legs that support this horizontal piece have been cut at the angle as well obviously.
So the monitor sits on that, then there is a piece along the front edge of the monitore, where the power button is, that keeps it from falling forward. Nothing in the back, but...i put more 2x4 rails in between the monitor and the sides of the cabinet to keep it from moving around - thats it...
yes, its pretty stable, i played golden tee tonight, not much shaking or anything...i can forsee some sort of bungee cord wrapped tight around the back of the monitor and to some hooks....
But again, the back of my cabinet is like 50% UNENCLOSED, so the monitor can slide right back out of the caibinet when i need to move it a long distance.
Thanks for the comments...my cab isnt perfect, but its mine, and an ABSOLUTE joy to build - i had a blast!
my semi-retired father has the tools, what a great shop he has down there....that bastard