I have a covered lift , still gets dusty under the canopy. Bass Pro has slip covers that are reasonably priced , don’t know if they would work in your situation? I personally would not leave my 621 in the water for a month.
Don’t they all come like that? Both my 621’s have that ratchet system with an additional big strap that goes underneath by the windshield and three straps that are in the back that wrap around the trailer as well.