Spent a lot of time studying how all of this goes together. I know the fit is going to be critical and I don't want to have to do this again.
Cut the access holes in the aft F631A channels. Agonized over the plans some more and triple checked the height and width measurements. Once I was satisfied that everything was perfect and with the channels securely clamped to the bench and drilled the center plate.
I then fit the F631B and layed out all of the holes per the plans. Once done I started drilling.
