Ok... this is not how I REALLY wanted to spend several hours but Scott's problem and solution has me concerned.
So it took quite a bit of trial and error to achieve a setup that had no error itself. This is what it looks like.
Note the support under the front of the frame... couldn't or wouldn't squeeze it tight enough in the vise to keep deflection and return to zero issues with the FRAME
So the net result was 0.0005 of rtz error up or down with about 0.010 of deflection in each test. The barrel protrudes 11" from the frame where I was measuring. If my attempt at remembering trig was correct, that yielded 0.15 moa of potential error which is less than a 22 pellet size at 100 yds. That was with the factory oring front support.
In this second pic, note the plastic shim protruding from the frame where the barrel is. I measured an 0.042" difference in size between the hole in the frame and barrel diameter. I found the tube in the pic to be 0.0205 thick and cut a piece to fit between the barrel and frame. It was tight getting the barrel in.
I tested 3 times with and without the shim and the results were pretty consistent. It was zero rtz error with the shim and 0.0005 without it.
The takeaway to me is that if you're searching for incremental gains in accuracy, there MAY be some to be had here but most of us will not be able to discriminate that amount of error... between ammo issues, wind, technique, etc.
As has already been discussed, it seems that Scott may have other issues and that he got improved results with the printed brace should point to the area.
This is not a pencil sized barrel but 15mm in diameter and is supported reasonably well in the middle. There really should be no flex or bump issues. For a comparison, the Red Wolf is a 23" long 15mm barrel that's held on one end and it doesn't suffer those problems.
Hope this may help,
Bob