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Lifting WITHOUT sliding is a good point. When people lift something large, like a spa, they'll tend to push into it as well. You should only need to lift it about 1/2" to slide the bracket under. I'd try a flat bar (small flat pry bar AKA wonder bar). One person should be able to step on the lat bar, lifting the spa, while another slides the bracket under.
Now 49 degrees
Just do what we do and hire some day laborers.Terminator