The cat is just fine on raising a hull, but you need to do some work on sealing that mast to prevent it from sinking. There are a couple ways to do this:

1) Make a tight-fitting top that rivets on and bed it extremely well. This is what the factory does and it holds up very well

2) Put a plastic bag inside the top of the mast and pour expanding closed-cell foam into it. When the foam has cured, cut it level with the top of the mast and seal it with some epoxy

3) Put a Hobie Bob on top of your mast

After you're sure that the mast won't sink, go out sailing and get a hull up. You can do it even in somewhat light airs by positioning yourself away from the windward hull. Some people go so far as to hike out off the leeward hull, though it feels very odd. Personally, I like to put my feet against the leeward hiking straps and lie across the trampoline with my head on the windward hull. When the hull comes up I'm sort of half-standing, a comfortable position.