Let's also not forget that those guys were not under fire!
Picture an RPG, or a M-60, or even a molotov hitting one of those vehicles. You'd lose the vehicle, and 2 squads.
So, in SP terms, sure, let you mount 40 guys on a tank - if they all become casualties when it brews up! In fact, one could say that the only glaring weakness in the SP passenger system is that passendgers don't lose enough men when the vehicle explodes.
"Tonight a dynasty is born." Ricky Proehl, then of the Saint Louis Rams. He was right! Go Pats! Winners of Super Bowls 36, 38 and 39.