Dave,
I own a 55 and I just happened to do spareribs last weekend. As such, it's still fresh in my mind. I hang my full racks from the very top rack, narrow end up, using the hooks I purchased from Cookshack. I have never done ten racks though, only 4 at a time. My take is that in order to hang ten at a time, you may have to cut a few ribs off the end at least for most of the racks. Otherwise, a good number of the racks will be laying on the wood box. Not all, as there is a gap to each side of the woodbox where you could have at least one or two hang. I can't say if the 55 is large enough to hold a full ten racks, even shortened to allow to hang straight.
When I do mine, I place the hook several ribs down from the top (for now, I use two hooks). This forces the top ribs to curl back down from the top. You will not be able to get ten racks in the 55 if you use this technique as the curled portion will take up space that could go to other racks.
Of course, my goal is to have some room between each rack so they can enjoy the smoke. I also try to avoid having the racks lay on the woodbox because I know it is hotter and do not want a weird differential between the ends of the rack, with one end cooked far beyond the other. The racks will shrink in length as they cook but I try to avoid the problem altogether by having the end of the rack near, but not touching, the woodbox.
I realize this post is long but I hope this helps. BTW, they turned out great last weekend, with my relatives all saying they were better than any they'd had in a restaurant. This almost makes up for all the mistakes I made during the learning curve. One more meal, probably of a brisket, and they'll be buying me meat for their weekend parties. I'll be one happy cook then as I'll be experimenting for free. This is huge fun for me.
-Grub