If you can't switch sides, why did you switch to the bigger side in the first place? If you didn't switch that day already nothing stops you from switching.
I switch to the side that is getting horded the worst. Numbers don't mean anything. I have seen a country with 40% of the server population LOSING because the other 2 sides were beating the crap out of them.
But fights don't last all day long. Fights only last about 1 hour maximum (from my personal experience). So after 1 hour the previous fights have died off and the side that was being horded is now on the offensive and a different country is now being horded on two fronts. Now I can't switch sides and join the fight because I have to wait 11 hours. So my options are to either join the mass of green planes, circle a virtually undefended base for 10 mins while everyone blows up the town, takes the base, and do it again. Or, I can sit in the tower chatting with my friends until something fun happens or I get bored and log off.