In reply to Stevie989:
I seriously doubt you'd get away with an 80 duffle bag in hand luggage, I get odd looks and often get asked to fit my bag in measuring device when using my 45l rucksack and that only fits in if it's less that fully packed.
The dimensions for cabin bags change from airline to airline and the degree to which they check changes not only between airline but between airports and also depends on how full the flight is.
Some airlines are a bit confusing for example. Easyjet have 2 sizes, smaller than one size and they guarantee it will go on as cabin luggage and up to the next size limit they may ask you to put it in the hold as a "gate bag" (still free but gets tagged at the gate and you put it in a pile that goes in the hold. any larger again and they'll charge you.