I hate wrong parts sold as right. My favorite response from telephone answerers is, "they never had an issue with them." Of course not! A truck won't fit inside the cubicle where that desk jockey works.
As far as the clamps, you cannot spread them, nor tighten them beyond their designed parameters without breaking them.
Shipping the cables back will cost you more than what the refund will be. Call the vendor and tell them that and that you are not a happy camper.
Keep in mind, they don't make the parts. They just sell them. They need, and should welcome accurate feedback. Maybe they will just send your money back.
