I am not quite sure how this thread turned into 150/150 performance and weight issues, but....
A Fuel Scan 450 is probably one of the most useful additions you can make....150hp or not. Long rang tanks or standard, knowing exactly how much fuel you have available is incredibly useful.
As far as the useful load, it's difficult to have a meaningful discussion with people who haven't flown a 150/150. Theory and academic discussion does not, in any way, prepare one for the way it behaves.
Like GPB says, you gotta get to know your own plane. If you never want to fly over gross, then don't. However, if flying over gross bothers you, then don't get a 150/150.
