I live in a warm part of Oz and have had no problems leaving any of my Hobie's on the carts as long as the Hobie bushings or similar are used so the crossbar doesn't touch, only half the weight is on the cart if you don't stack gear on it.
For my balloon tire beach cart I place a plastic crate under the stern, not lifting totally but just taking most of the weight off the tires to avoid the cold concrete forming any distortions in them.
Recently I invested in a new cart that balances and cradles all my boats perfectly with parallel supports that distribute load.
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