it ruins the rounded look that you see when you use the NA (and late model TT) TBL on the hatch. I'd like to see an implementation of a flush mount that keeps the complete NA TBL piece. I don't know if i'd like it, but I'd like to see it.
The graphic in TwinZ's sig shows what I'm talking about quite well. The wingless Z has the nice complete rounded black tail light section while the Z with the flushmount wing just doesn't look as smooth.