According to the book Kriya Secrets Revealed who claims to pass on Lahiri Mahasaya's authentic teachings, it is safe to go up to this point and the author adds that the reason to go this high is because of Ajna knot.
I'm doing AYP's SBP and yesterday I went up to bindu visarga (cowlick) and felt more purification going on and a more intense vibration on third eye. Has anyone tried it yet? Do you think it is dangerous?
Thanks