Hi, i'm trying to decide which to put on my new Rem870P 18" 12ga shotgun (3" shells). To be used for HD and occasional fun indoor/outdoor target practice. I definitely want a light, and then the question is whether to include a laser. I want to do it right the first time so i don't mind paying up $$ for quality...that's why i've kind of narrowed my choices down to Surefire x400 light/laser vs. 618LMG light replacement forend. The 618 gets tons of great reviews online. It looks very user-friendly and easy to operate under duress, with the switches right there on the forend grip. I haven't seen as many reviews of the x400. Firstly, is it solid enough to put on a shotgun or is it more suitable for pistols only ? I guess my main concern would be having to frequently zero the thing. Plus, i'd have to mount the x400 somewhere...any recommendations on an aftermarket forend w/tactical rails ? fyi i'll have an Aimpoint Pro red-dot mounted on top. The gun also has rifle tritium night sights. Thanx in advance for any advice and opinions !