I always cut my racks of baby backs in half for my 1400. I can arrange them in brick fashion on the racks (one vertical, two horizontal) on one rack, them two horizontal and one vertical on the next rack. I think it makes the heat and smoke flow around then, rather than straight through, but I also put everything in, set the temp at 225 and close the door, and leave it closed for 6 hours. Everything seems to be done pretty similarly at the end of the time, but, YMMV, since I'm not doing St Louis style.
I believe in catch and release fishing. I don't want to EAT 'em all, I just want to GREET 'em all!