Whether it's a frame or a complete bike, the price will depend on "dimensional weight", i.e. size of the box, not the weight, and shippers do measure; so there's no point in trying to fudge that when getting quotes or purchasing a label. If a box bulges, you'll probably be charged for the rectangular prism the item will fit into without sticking out (they have lasers too). It's a business. Not a ton of experience, but I have used both BikeFlights and PirateShip, found the latter to be cheaper when I've comparison shopped. Haven't had anything damaged, but I pack carefully, avoid corners and add more layers to protect something vulnerable on the larger faces, even if that increases size a bit.