Hello Leo
I have made the same experience with the CMK Schmalturm. The Schmalturn used on the Panther F and the (paper-) Panzer IV were supposed to be the very same turret. CMK got it waaaaay to small, so it might look ok on a Pz. IV, but simply looks odd on a Panther chassis.
Besides beeing to small the cupola is also incorrect. Gaso.Line could ba an option but it uses the cupola from the Panther G kit so it isn't right either, I'm afraid.
I had the same idea a while back, but the lack of a decent Schmalturm led me to use a G turret on a F hull, as shown in the picture.