Planes / Spaceplanes unflyable!

I have been trying to create usable planes and space planes for quite a while. I finally get the COL/COM balanced well, and I cannot yaw without pitch and roll being induced, and all rotations seem to induce rotations on the other axes. For example, when I try to roll 45 degrees left, I get right yaw and down pitch. Once I get on a heading, I have a VERY hard time turning. I thought I was designing them incorrectly so I downloaded an SSTO from Marcus House's page and tried it....same thing. Also, I used his kOS script to attempt to get it into orbit and the engines shutdown due to overheating well before the closed cycle starts.

I suspect I have installation issues. Either my dual core laptop (which seems to be pegged most of the time) just can't do it, or I have some difficulty setting set to hard. Any ideas? I am very frustrated with the planes.Planes / Spaceplanes unflyable!

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