John Smith wrote:
"In other words, what set of formulas would give you length, conductor
spacing, gamma capacitor value----?"

It looks experimental to me.

My ARRL Handbook says that the T match has an advantage in that a pair
of transmission line attachment points equidistant from the center of a
resonant wire has a resistance between them. Therefore it is possible to
choose points which match the line Zo. Problem is the physical distance
between the attachment points probably does not match the line spacing.
The handbook suggests a T match made like a folded dipole with
single-wire extensions at its ends. This looks as if it would require
experimentation.. It seems suited for parallel-wire lines.

The gamma match seems to be similar but an ubbalanced scheme where the
grounded line conductor is attached to the center of the radiator and
the ungrounded conductor is connected to the wire at a distance from the
center of the radiator which results in a low SWR on the transmission
line. A variation treats the gamma match as if it were a shunt tower
feed arangement.

The gamma match becomes a feed loop containing a ground path. The feed
loop is sized to that required for a resistive component which matches
the Zo of the transmission line. The loop inductively couples the
antenna with the transmission line. The loop`s reactance is always
inductive and can be tuned out with a series connected variable
capacitor.

It seems a good cut-and-try project to me. Maybe perfect for Art Unwin.

Best regards, Richard Harrison, KB5WZI