1) First no stamp paper required
2) Registration under registration act is optional but strongly recommended .
3) Video of registering recomended is also good idea in future . Recording should be done by independent witness. Regarding taking digital video I feel some one should give inputs from Evidence Act :) here
4) To reduce conflct in future I would suggest all legal heirs of person making will should be made witness additional two indepent witness . Plus one or two Dr. certificate that person was mentally stable to make will . See this are precaution so will is not challenged in future . or declared illegal. Even when all are witness after death of person they can not knock court and even if they knock that won't surview .
5) I heard some billioniars famiy of our country their they had family meeting for long time how to settle their various industries and will was made in presence of everyone and everyone was given charge of respective large scale industry , as if separation was done before death. And person who did is chairman or final controler. So will was just legal document to save tax and further dispute.