Needle Selection for SU

[Matthew P Johnson <spriteguy@juno.com>]

Has anyone ever tried selecting a needle for an SU carb after modifying
the engine?

The way I would like to do this is by using an Exhaust Gas Temperature
sensor and gauge to determine the optimum fuel mixture.  What is the
optimum temperature for max. power?

Is there rule of thumb based on EGT for determining how much the needle
diameter needs to change to get the right mixture (e.g.; for every 100
degrees from optimum temp change the needle diameter by .001"?)?

Help would be appreciated.
Thanks,
Matt