I got to the workshop today and cut a pair of bases and vanes to go with them. I made provisions to test the 60 degree angle as well as a 30 degree angle and even a center vane for if the outer vanes don't come all the way together. I also did vanes in 1, 1-1/4, 1-1/2, and 1-3/4" lengths. The slot that holds the vane at the base is 3 times longer than the tab on the vane, so the vanes can be adjusted forward/rearward to adjust the opening between them. This will allow for a lot of variation.
I did up two sets. Typically I will test with one speaker with the RTA, then apply that modification to both and do lots of listening.