I was told to inform people to avoid doing the practices on the JoS they are wrong and cause problems.
On Kundalini, the actual Kundalini practices are dangerous and can cause damage to the body. A person should only do this if ready. I will add in the East people do years of pranayama's just to develop a basic ability with them.
I will add there is no Kundalini serpent, this symbol in the east is just the spinal column and brain they will tell you this in their own works and lectures.
Kundalini takes years of daily practice to develop the result. Its a life time practice and its dangerous and intense.
A person needs to be careful with Kundalini.