Multi wall problem

[rhots]

Hi folks, still getting used to SU. I am trying the multiwall plugin which is awesome.
But when creating an opening, some walls, (created from "lines to walls") get a "bumpout" rather than an opening. I have attached the dwg in question.
Any help would be greatly appreciated.
Thanks,
Rick

Sketchup 8 win xp pro

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wall test2.skp

[rhots]

Answered my own question. When drawing the lines I was in plan view which made my picks come from the top of the existing walls. So I ended up using a negative value for the wall height, which worked fine to create the wall, but apparently it screws up the opening operation.
Thanks,
Rick