I spend most of my time making SSTO space planes, and I tend to have my own rules regarding what IS and ISN'T allowed for a "valid" space plane. For example, part-clipping is ok, but actually embedding one part inside of another is not. Air intakes are obviously necessary, but at no more than a 2:1 intake to engine ratio. I'm curious as to how the rest of the community defines "air-hoggy". Do you have a specific ratio that you won't move beyond before you consider it "cheating"?