I have one of the technically oversize F'lite suitcases, but I have yet to be charged for oversize from the airlines.
It's easy and quick for the airline agent to plop your loaded suitcase on the scale. I've had this done every time I've flown with the F'lite and my Bike Friday. So I make sure the total weight doesn't exceed the 50 lb. international weight limit. If it does, you can bet that the agent will whip out the tape measure and check for oversize as well as overweight. I've never had the agent check for oversize if the case doesn't exceed the 50 lb. weight limit, tho, because it's close enough to the 62" total dimension to not look obviously oversize.
If the airline counter is crowded, the agents are much less likely to check for oversize as long as the case doesn't exceed the 50 lb. weight limit. There have been times I've gotten to the airport early and actually waited for the airline counter to get crowded before I approach.