Umm I'm not saying you won't find an check in agent who would but I would doubt this very highly.

I wouldn't count on it. You will have an easier time packing your stuff into an oversized piece of luggage as they have scales to weigh the stuff but rarely will they take out a tape measure and start calculating linear inches. I always find that 70 lbs is a heck of a lot of weight thus it is the size that is limiting to me more than the weight of each piece.

Let us know how it works out but I wouldn't plan on any waiver.