Advincula Sensei was one of the many US Marines who studied with Shimabuku Sensei in the 1950's.  But.. Advincula Sensei returned to continue his studies with Tatsuo Shimabuku on a great number of occasions.  Sensei Advincula started the Isshinkai organization in which he teaches the latest evolution of techniques as taught in the later years of Soke.  At the same time, Sensei Advincula is the single most knowledgeable of Shimabuku's students since he spent the longest total time studying with him.