All mine are in parallel, i have trees which shade between 11 and 2 so parallel gives more power during that time , as said on a boat cable lengths are not long enough to make a difference unless you are using 12 volt panels , my opinion is don’t , they are too expensive and too low voltage unless series connecting , victron mppt for example doesn’t even turn on until 5 volts over battery voltage it’s all too tight imo , give yourself some headroom , 24 volt panels much better with an mppt , reserve 12 volt for pwm controllers .