I have a similar sized shed (8x12 with 3.6 to eves and 4.2 at the peak), depending on what your hoist is will determine where you can put it, I have a clear floor hoist and I had to put it 2mtrs from the side wall as the height will not allow it to go any closer (bloody council restrictions), as above, if you have a standard hoist with the hump you may be able to go closer to the wall but it may restrict the height on some vehicles.
My hoist is just over centre, but I can still park a car beside it with my set up, I could not see a spot where a 4 poster would fit and get clearance when a car was on it and up.
