I went down this road with disappointing results a while back. Since 129 was sketchy on my 1000.2, I figured I would buy the W bracket and use only the center position to grab 129 (not realizing the gain would be no better). When I discovered the lack of improvement I started some trial and error to figure out why I was not seeing an improvement.
To make a long story short, I discovered that a D500 with I-bracket got better gain than a 1000.2 using the center position of the W bracket. Aside from the focal point issue mentioned above, I believe the fact that the 1000.2 is actually smaller than the D500 (on the vertical axis) contributed to the results.
So, my spare parts supply continues to grow as I slowly but surely purge my ignorance!