You might consider, not all that will be buying your system would have a 18.5" barrel and if the rail system is too long it will not be practical for special operations requiring shortened barrels (Benelli supplies a 14" barrel for this purpose). Just something to consider if you intend on marketing it to Military or Law Enforcement. Looks like a good product so far. But seems like it will be heavier than tolerable with all the ammo mounted on it.
IMHO