6 rounds is good, 8 or 9 is better......One hopes you never need to fire one, but I always figured, once I had no other option, the more lead I can throw the better off I am....12 guage Mossberg "special purpose" (8 rounds of 00buck, 3" magnum, 15 pellets per, sidesaddle for 6 more rounds) aughta keep their heads down, until I can grab the CM-11 carbine (4 32 round clips fulla Black Talon +P+) and/or the SKS (4 30 round clips, including the "special" one w/ alternating AP and incindiary rounds)...I guess if THOSE 250 or so rounds haven't stopped them, I'm SERIOUSLY screwed!
Seriously, a 6 round shotgun is good defense weapon, nonetheless....The sidesaddle is a good, inexpensive solution..just in case!!!