Paul,
I think it depends on your definition of 'fits'.
The armrest I have is from a 108 and is the exact same length as the pagoda's wooden tray (measured from the outside of tray edges). The width is identical from the rear, but about 5mm wider on each side from the front (again, outside measurements of wooden tray).
Didn't have my camera handy, but I'll take some pictures tomorrow alongside a spare pagoda center tray I have.
On the other hand, my 111 coupe center console armrest is tapered such that whilst it sits completely within the wooden tray, the upper portion extends out to cover the top edges of the tray. Of course, this is for a 250se, which still had the wooden center tray; the 280se coupes/convertibles all had plastic center trays (ugh!). In fact, the 280se shed quite a lot of wood and chrome. I don't understand why they are the most in demand (unless you have a 3.5) ...but I digress.
Waqas in Austin, Texas