As all builders know the current utility arms do not clear the skins. Filing away at the skin changes the shape of the opening and thus the visual design - a cardinal sin in my eyes! It might be the easiest way, but dont do it!! Instead get an electric file and make an extra angle on the inner part if the arm. That way it retains the shape/look when closed.
Here's the top snap. The secret is to have one of the three snaps mounted to the opposite side as the two others (over/underneath the frame rings) That way you eliminate any vertical travel as well as help guiding the snaps into position when fixing the skins.