On this subject I'd like to contribute with experience gained from a recent reserve ride of mine.
I deployed into linetwists and initially my Sabre2-135 (at WL ~1.6) was reasonably stable. As I grabbed the risers and started kicking it almost immediately went into a diving spin making further efforts to solve this malfunction pointless due to the heavy G's it was pulling.
The spin - in my opinion - started as I started kicking. In a linetwist configuration with only 1-2 twists it is possible to pull one riser/linegroup down without it being able to get back up. I cannot say if it happend because I was pulling on the risers or if it was the sudden shift of my body in the harness.
However, I believe a few twists could turn out to be more of a challenge than many.
Attached you will find a picture of my spinning Sabre2 with the uneven risers. The video is also available here http://www.skydivingmovies.com/ver2/pafiledb.php?action=file&id=5998
Drop