Yep, I did it! No problems at all. Here's a few pics...
I cut the one access plate for a template (you will have to order the access plate cover with no holes in it from Van's).
Here's a shot of the outstide of the baffle with the stiffener ring riveted in place. That ring is made from the one I cut out in the above pic.

And inside-
Sender unit in place-
Access plate with no holes (part number T-411)-
Rear baffle after complete-
Hope that helps!