symmetrical or non-symmetrical, or flat bottom or not, there should no difference in the reading when you flip the meter end for end on the wing, as long as the initial set up of the meter is done correctly and both attachment brackets are identical in all aspects. if you are getting different readings, your level is not set exactly right or there is a difference in the shape of the "V" in the attachment brackets. one other spot to check is that there is no play where the attachment arms mount to the beam. if play exists there, it changes the relationship "V" to datum by changing the included angle of the "V" in relation to the wing's chord line.