I have received the same update. I haven't installed it yet, but I did trim out the pattern and test fit it. Didn't look right - then I realized Van's as updated this section of the plans and I was looking at the older revision. Look at page 9 here:
I think that helps to visualize what needs to be removed. In particular the circular notch in the F-01201E's needs to be enlarged/moved further back towards the firewall (I was trying to line up the notch in the pattern with the existing notch, and that didn't work).
If you look at what needs to be cut from behind, I think you'll see the mating portions of the F-01201E's - and likely the trimming needs to match up to these lines and not remove any more of the F-01201E than just the large tabs.