Golf bags don't get hit with the oversize fee. As mentioned before, they will get you if it's overweight.

As far as the T+C stuff (14 clubs, 12 balls, 1 pair shoes) I've yet to run into an agent who was interested in the contents as long as the scale said the correct number. I've frequently carried an extra club or three, ooodles of ammo, and still come in under 50 pounds - with a Bag Boy rolling hardcase. What you can stuff in will depend on what your case weighs empty.

You may be asked for a liability release (yeah, I know it's stupid on a hardcase) and if so it's either sign or the clubs don't go. It IS US policy to waiver all golf bags - but enforcement is all over the yard. I've had different results at the same stations - and when I inquired, one of our helpful FT members with a connection in Cust Service got me the official response - which is they want waivers on all golf bags.

And good choice on the hard case - in observing rampers loading planes, it seems that large or heavy objects get treated with disdain at times, (large + heavy) = Disdain squared