1- S. Sistani has not given any fatwa, neither positive, nor negative in this regard. Hence, we can not say it is jayez or not jayez.
Since he do not have a statement about it, you can refer to someone else, and follow his fatwa.
2- This thing was not practiced in the Imams days. Hence, there are no narrations about it. Therefore, no one can say it is haram.
Saying it is haram depends on certain criteria, such as:
1- If it leads to bad image of Shia.
2- If it leads to harm your body seriously.
3- If it harms someone else, like those who are practicing it with their kids.