I've got a flat-top AR-15 that has only iron sights. I've got a YHM flip-up front sight gas block and a picatinny rear back up iron sight, also YHM. I'd like to add a scope, but so many of the options will take up the entire real estate of the flat-top rail. Is losing the rear sight worth having a scope? I'm thinking of a 1-3x-30mm scope by Barska, but I am open to thoughts. There are risers, etc., but I don't want to raise the scope too high to mess up the cheek weld.