Going back to the original question I always go by the fuse ..And I just go by eyeballing it...I stand back and when it looks level it usually is awufully close .. Very often the wing has positive incidence and very often the horizontal stabilizer has positive incidence too so going by the datum line is the best way to go ..I have just started using the Vanrssa Rig and am finding it fantastic...I was sceptical at first but I am converted now..If anything I go for a tiny bit nose heavy just to be on the safe side . When the plane is in the sling and looking level I will look to see where the plumb bob is pointing..I will adjust my weight accordingly ..