Sconnie,
6-10? that's probably pork butt. what can you do with ribs? can you do 4 Baby backs or only 2 full racks?
6-10 people would be a 14 pound turkey, brisket, or pork butt. I have the older rack guides, which only have 3 rails, so I can do 3 racks of baby backs, one rack of ribs per shelf, cut in half. It looks like the newer #1 has 4 rack guides, so in theory you could do 4 racks of ribs on 4 shelves, but you'd probably have to rotate the shelves, because the lower shelf looks pretty close to the smoke box. I don't know about you, but 3 baby backs would feed 6 people, unless they are big eaters. With sides, I usually end up eating just 3 or 4 ribs. But there are members of my family that could probably eat a whole rack of Baby Backs. As far as St. Louis spares or full spares, I do two, by doing 2/3 rack on shelf 1, 2/3 rack on shelf 2, and the two little 1/3 pieces on shelf 3. You do have to cut things into two pieces for ribs and brisket, but since I cut them up in the end to serve anyway, I haven't found this to be a problem, and the quality of the end product seems just as good. It just adds for a few more barky edges if you like that stuff.