There is a circular area in the buccal slope of the palatal socket, in which the bone looks thin (purplish: presumably the sinus membrane underneath, Fig.5,7 (blue circle)).  It appears that the palatal slope of the buccal socket (red dashed line) is the most appropriate site for osteotomy in this case (Fig.8).  Preop CT would show bone morphology.

Buccal Socket Osteotomy Last Next Xin Wei, DDS, PhD, MS 1st edition 07/10/2017, last revision 01/04/2019