I am planning on purchasing an Aimpoint Comp M2 that I will be mounting on a Bushmaster M4 flattop upper with ARMS Swan Sleeve w/ backup sight. My question is, would I be better off using the Aimpoint Rail Grabber or the ARMS #22M68N mount? Naturally, I would prefer to use whichever one is sturdier. Will I have to detach the Aimpoint in order to use the backup sights, or does everything line up just right so that I can simply obtain an "iron" sight picture while looking through the Aimpoint? Thanks for your help!