I saw hints that the application of the tapered line matching section was
to a HF off centre fed dipole, and an assumption that as a multiband
antenna, it had a feedpoint impedance of close to 200+j0.

Most users of OCF dipole systems are expecting to be able to use the
antenna on many bands without an ATU, and accept significant tradeoffs in
peformance for that objective.

It is unlikely that the feedpoint impedance of the dipole itself is
sufficiently tight to worry too much about the broaband peformance of a
tapered line matching section, much less the practicality of constructing
low loss tapered two wire lines with Zo approaching 50 ohms.

It is only when a system perspective is taken, that some of the component
level discussion seems to be an interesting issue, but poor application.

Owen