I have a single 90watt panel connected to a charge controller. The cc
has the capability of adjusting the voltage at which it will stop
charging the 2 4D gel batteries connected in parallel.

Any comments on what voltage should be set to stop charging?

My Truecharge 20 charger, when set to Gel, goes into trickle at
13.6volts. Is this a good set point for the charge controller?

Alec