Front sight sunshade

I have a D75 with a Duo iris front sight. The sight currently has a sunshade that is on the muzzle side iris. Question is what side of the front sight does the sunshade work best? This is all new to me, I can't move the existing sunshade I have to the rear iris to try, wrong size. I would buy one to fit if there is an advantage to having it on the breech side of the sight.
Opinions?