Mwr0707, do you recall if the soundstage of the F's was located primarily behind the speakers when listening straight on axis like the CLS series 3 drivers?
Maybe there is a difference here that you perceive as "more restrained" upper midrange?
With the Walsh 5 S3 drivers, the "perspective" adjustment, which corresponds mainly to midrange, I believe can be set to "close", "medium" or "far". The "far" setting seems to move the soundstage more back behind the speakers when listening dead on.
Unfortunately, I do not know which settings on the Walsh5 S3 match or come closest to matching the sound of the 300 or 200 drivers, which do not have adjustments.
You might want to pop John Strohbeen an email and get his input.