From the Optima battery
An Optima is an AGM battery, not a gel battery or regular flooded acid battery.
Most modern battery chargers, including OPTIMA Chargers, have a built-in AGM charge setting, which should be used for your Optima. If purchasing a new battery charger, make sure it has AGM compatibility or a separate AGM setting. Do not use gel or gel/AGM settings, as this will not fully charge an Optima and can damage it over time.
Based on this, Thom, I would recommend NOT putting the converter into gel mode.