Developer XVortex has released an application that lets you easily create .PKG files for use with the PS4, this update is the fourth release and it gives support for PlayGo titles, here is are the changes in this version:
All (except system) files are assigned to all chunks (you may need to reassign them manually).
playgo-chunk.dat is dumped by flatz method to dump\pkg\playgo.txt (for analysis and manual gp4 editing).
Minor changes in .elf processing.
Here is a guide on how to use it from ModConsoles.fr: