sizing oil cooler, biggest or big enough Options

[machina]

Do most people just use the biggest cooler they can jam up front, like a 22x6x2 or is there a way to calculate how much heat capacity the cooler should be able to remove at a given speed?

Those things start to get pretty heavy and expensive. Would one of the more compact fluidynes work on a 2 liter motor in the summer? I noticed paul (mr lightweight) has a relatively small cooler on his car.

Thanks,
dr