Definetly a gusset is in order on the outboard side of the verticals. A while back I was thinking of building one of these out of wood for picking loads out of pick-ups or trailers. But if you do build one of these I think I would get the trolley for the hoist first and size the beam to that
The optimist says the glass is half full, the pessimist says it's half empty. The paranoid in me says somebody put a hole in it.
Remember pessimists are at heart opptomists. They know things can and will get worse.