It’s easy to forget nothing is permanent. You can print really well as it was designed, and then improve it based on your results.
You don’t really need 3/4" right angle, just a small piece of plastic to dampen the vibration.
If you put a little right-angled piece of plastic and screwed it into the XY frame and the base, then it would stiffen it right up. Here’s a pic of what I’m talking about, replace that little square with a piece of plastic (it could even be the “Brace.STL” from the MP3DP). Do the same on the back. (((BTW, I think Ryan suggested this first when I showed him the base)))
Another thing I was thinking about if you want that extra few mm in the Y direction, you could move the XY Frame to the outside, instead of the inside of the corners. It wouldn’t look as good, but it would give you a tad more stretch.
So in this pic, Just leave everything else where it is, and move the board to the left side.
And thanks for trying my base. AFAIK, no one else has done it. I keep meaning to build a box underneath it for my CPU and RAMPS, but everything is fine just floating around, and I’m otherwise still pretty busy.