I had a golf bag in my trunk and someone put a rigid 20-30 lb suitcase in the middle of the bag, and a 15-20lb bag on the heads. I drove around for a while on a rough road in heavy traffic, so lots of hard turns and potholes. It looks like the club shaft that was directly beneath the suitcase is slightly bent, but it's hard to tell.
These are steel, regular flex shafts.
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