I would just like to comment that though J1 and J2 are the same, not all commercial and freeware software are able to
import J2 implementation of jpeg lossless. J1=UID 70 and j2= UID 57 should be compatible
and interchangeable, but unfortunately UID 70 seems to be more universally accepted jpeg lossless transfer syntax implementation.
I would have wished jpeg J1 was the version you choose to retain. So that Kpacs and efilm ver 1x to 2x can import them directly.
see comment of David Clunie.