Degrees of freedom

The universe may 'arguably' be 6 dimensional but we all race boats in our petty 4 dimensions (if you include time). At what point is a physical dimension ment to be a variable?

Before you fall over patting yourself's on the back about how many VARIABLES you can deal with consider this - when racing a GP over a Laser you have more boat speed related variables to consider, does this make the penalty for miss calculating them better or worse. Base jumpers may only have 1 variable to deal with, when to/or not to pull the cord.... if they get it wrong will they just get wet, or will they die.