I'm having some trouble understanding the PLC manager, and I'm hoping someone can offer some guidance. It's been a recurring, repeatable issue for which I haven't been able to find an answer.

This is the most recent project I'm working on. PLC1 is the PLC I actually want to use, PLC2 I just added as a test. PLC1 has a manufacturer component added at the top level, with expansion cards underneath it. The main problem I'm seeing is that when I add expansion cards (modules) the first two or three come in in the correct order, but then the order goes all random, with no rhyme or reason. I've named the modules with their position in the rack (it's a micrologix, so there isn't really a rack...) and this shot shows how they go all wonky.

Even when I manually change the Card Position and Slot, the PLC manager overwrites the position to something completely random:

I created PLC2 as a test, thinking that maybe there HAD to be a rack associated in order to make things work. Except I can't really test that, because I get the following when I try to add more than one module to a rack:

I've checked everywhere I can think of and I can't find anything that will allow me to define how many slots a rack should have.

So I guess the question is two-fold: Is there something I screwed up in adding the modules to the PLC without a rack, something that's making me unable to put them in the proper order? And is there a way to define how many slots the rack should have (good to know for the future, I do a lot of work with controllogix as well)?