Thank you, That did help a lot when making straight runs in a L shape. Maybe I can keep what hair I have left. 
Still having troubles when running them on a angle to form a V. But I don't run them like that very often.
I haven't tried what I'm about to suggest but reading your post gave me an idea. How about placing temp walls where you want the sofa, then place the sofa and delete the walls? I'm going to try it to see if it works, but perhaps someone already knows the answer.
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Edit: Just tried it. it works. Turns out, it was easier to start with the corner piece. First, make the walls, then set the sofa section that will eventually become the corner link, then attach the side pieces. Lastly, delete the temp walls. Depending on how much stuff you already have in the house, it may take some finagling of existing pieces before you can set up the temp walls, but overall, using temp walls does seem to work. I imagine halfwalls would work, too, and they might be easier to deal with. At least you can see over them.