Inventor - shorten chassis segments?

[smcmahon]

OK, I'm sure this is a noob question, but I'm very new to Inventor. Like 3 hours new. I'm pretty good at teaching myself, and have been through some tutorials already.

I've made a new file in which I've placed a bunch of C-Base chassis channel segments, along with the corner connector things. I've got it all constrained together. The thing makes a big square though, of course, since all the chassis bars are the same length. I want to shorten the two horizontal bars so I end up with a "long wheel base" rectangular shape.

I've been digging all through everywhere trying to figure out how to isolate one component (or these two bars in this case) and simply change the length of it. I want to make it like 10" shorter or something.

How do I do this?