Based on our studies in the nmrlipids.blogspot.fi project, there seems to be different glycerol backbone isomers in different leaflets in the configuration delivered with this package. For more details see: http://nmrlipids.blogspot.fi/2014/09/about-glycerol-conformations.html

Structure having the same isomer in all lipids can be found here: https://github.com/NMRLipids/nmrlipids.blogspot.fi/tree/master/POPCgaff