Oh, is that so ?… With the GND between P2 and P3 I have noticed that the phase differential goes towards 180 as each of the Z goes towards 0.
The half-dipole .s1p’s that are being used are just the initial .s1p file (real antenna measurement, full dipole) where the impedances have been halved.
Definitely going to use an ideal 1:1 transformer with the initial s1p file.
Thank you for the replies, much appreciated!