I do love that vid, however I really doubt Jimi could play a drop tuned 12 like Lead Belly. There are no films showing how Lead Belly did what he did. There are more audio examples out there. Uncanny playing. Drop tunings down to C were common with 12 string guitars as there were no light gauge strings back in the day. The earliest 12 string guitars were not braced to withstand the string tension of standard tunings. Leo Kottke is one known player who could have possibly have gotten close. There were / are no doubt others who never "made it" who could pull that off.