Hate to always sound like an engineer (I R One) but brackets such as you posted need to be disigned and built according to the loads they are transfering. The size and number of lag bolts on the vertical post would be determined by the anticipated load coming down the rafter or sloped beam. If it is extremely overbuilt you can get by but how do you decide what is severely overbuilt or what is the bare minimum required? Sorry, but that is how I think and how I was trained.
Carry on!
Iffin the roof falls in on your tractor,....it wasn't over built!