Curious that you deleted your post as I was about to reply to it. FYI, Rod Cross
is a retired physics professor from the University of Sydney (but still appears to be member of the university staff). He has a PhD in plasma physics and is also considered an expert in sports mechanics and forensic physics. TWU (Tennis Warehouse University) was developed by Rod Cross and Crawford Lindsey.
These 2 men co-authored Technical Tennis
which talks about spiralspin
in some depth. They also collaborated with physicist, Howard Brody to write The Physics and Technology of Tennis
. In the following TWU article, Physics of the Tennis Kick Serve
, Rod Cross talks a bit about gyrospin (aka spiralspin or corkscrew spin).