Thanks to Diego with support. Got back to my e-mail within a couple hours with the following answer - huge help:
Hi Dave,
You are correct, you will need to loosen the 4 screws holding the spindle brackets up to the next set so that your VFD spindle is located at in the proper position. The holes should be aligned so that you shouldn’t have to worry about the brackets being squared but it never hurts to check with a level.
Let us know if you have any questions or require any further assistance with this.
Regards,
Diego