Just a couple of thoughts on SG for HD:
The need for slugs is vastly over rated, in every state the right of the citizen to use lethal force is limited to defense, castle laws are nice, but even those do not allow a citizen to use lethal force against a person who is no longer a threat-that means a retreating threat is not a threat unless he is shooting at you while he is retreating. Shotguns are close range weapons, if the BG is so far away that you need slugs to reach him, you are probably out of danger, and out of your right to use lethal force(mostly, not always). The rule I teach? Never but never shoot at a BG running away.
If you live in the wide open spaces and a slug wandering around the countryside is no big liability and you want to use them in lieu of buck, no problem. The real issue with using slugs as a primary load is over penetration and the subsequent liability.
the KISS system is always best, as mentioned by several folks above a light and some extra ammo is all that is needed. I prefer extra ammo on the gun to be in a butt cuff, easy to remove the whole cuff, and no bolting stuff to the side of the weapon. Slings and heatshields/handguards are just tactikool fluff. A sling is for only two purposes: 1. When standing a fixed post for a long time(as in a roadblock) and you need to keep the gun in a ready position. 2. For humping the weapon long distances on foot. In HD the sling will catch on anything and everything, and provide a really neat handhold for any BG who gets too close(a SG IS a short range weapon, yes?).
A heat shield or handguard was originally to protect the off hand from a hot barrel when going to the guard position with your bayonet fixed, where your off hand is placed on top of the barrel. So unless you are planning to shish ka bob your friendly neighborhood felon, you probably don't need one. In any case your hands should be positioned at all times to operate the weapon.
OK, EOR (end of rant).