I calculate 11.45 amps for each of your 4 220V circuits. If you increased your 210W panels to 300, I get 16.36 Amps. Since 12 GA wire is rated for 20 Amps, I don't see any need to change the wiring. What is the purpose of your change? Do you need more power and have no room for more panels? Are your panels getting old?

Thanks for info. Panels are old but have no significant deterioration in output yet. Thinking ahead. House uses a lot of electricity. Less work to upgrade to newer panels on existing infrastructure than to put in new proper brackets/flashing and rail. Also, choice sun spots(south & unshaded) were selected for existing panels. Any additional areas would receive less daily sun. Of course, replacing panels mean gain is only difference new/old panel as opposed to full addition if add panels. Watching technology improve, would only upgrade if power output & cost are sufficiently better. Improvements over the past decade are already quite impressive.