Robert -
I think you are close to right, perhaps a year or two too late. As you say, the change seems to have been phased in over time and across models.
My 2002 2720SL (bought in Sept or Oct 2001) did not have wood in that area, but instead had aluminum channel.
There is a discussion here, including a number of photos from Larry Loo, whose TM was the same model and year as mine. I posted some pics as well, but they seem to be gone.
http://www.trailmanorowners.com/foru...read.php?t=537
Bill