I finally got back to this project. I removed the frame and old solar panel, and put Starboard in place of the panel. (Two pieces of 1/4" thick Starboard.) For our current purposes of bay and near coastal sailing , that is sufficient.
If I want to re-add a panel later, I can either remove the Starboard easily, or attach a new panel to the stern rail (which is much closer to the batteries anyway).
My final analysis was this -- The old panel looked like crap after years of being stepped on. And when removed, I cut it open (just for knowledge), water came out of it. Also, during the peak of the day, the boom shades much of the panel, so it's not an optimal location -- looks great on paper, but not the best in practice. I chose Starboard since its surface has a diamond pattern in it, which is a non-skid surface when standing in that area, and it was a much cheaper solution than another solar panel.
As said above, the Starboard can be removed later and/or a panel added to the stern rail.
Thanks to everyone who offered their own experiences and ideas.