Hi guys, I slapped a Black Aces Quad Rail on my 590A1 along with a red dot and was curious as to which flip up sight would best suit my gun? I've been doing some research comparing Fab Defense V.S. Magpul MBUS, and I think I'm leaning towards Fab Defense for the tool-less adjustment factor. I've also noticed these sights are made for the AR platform... Will they work on my shotgun as well? If not, are there flip ups dedicated for shotgun? (I am used to the old school bead sight - not this tactical stuff. lol) Do any of you run backup flip up sights on your shotguns?