Eddie,
from what im looking at in this latest model which may not be what it looks like from my side,
the dimensions drawing with pencil annotations could be giving you the wrong idea of what a gainmaster is,
the red foam coax goes from the so239 under the choke all the way up to the feedpoint at the middle of the antenna, electrically there is no 2.5cm gap in the braid where the stub attaches,
i posted images on here of the stub connection board and feed-point board years ago but can't find them,
if you use the tl function to make the coax parts in the model you must add a 3rd wire in parallel with the coax so it carries current and radiates,,
if you did that i can't see it here from the model images.
have you got coax made with the tl function plus a 3rd wire to simulate the outside of the braid that i can't see Eddie?
it looks like a wire dipole but that does not mean that's is what i am looking at as i never saw a coax dipole in nec with the extra wire to simulate the braid.
