Laast night I decided to do a little experiment.
As Kennel Linux releases have various ways of accessing the root file system in a running an installation. One of the methods being Pseudo Full Install. In this type of installation the rootfs is copied the the upper changes layer, not requiring to have a rootfs layer(doesn't even require a dummy rootfs layer). The writing to the upper_changes directory can still be controlled and saved or not saved as desired.
As the dpupbw64save directory contains an upper directory for changes, I decided to make a new install, where the puppy_dpupbw64_10.0.9.sfs is extracted and the resultant directory being renamed to upper within the dpupbw64save. To accomplish this install, DPupBW64 still requires a puppy_dpupbw64_10.0.9.sfs. I did a bit of swapping, using a save folder containing only basic initial setup details, timezone, wifi network setup. I edited the save folder then ran mksquashfs. Basically reversing the normal process, this was just for expedience, I could have just created some sort of dummy puppy_dpupbw64_10.0.9.sfs.
The resultant install runs the same as my normal frugal install. As part of the experiment I updated the included Firefox ESR 128.5.2 to the new version 128.7.0. Saves and boot/reboot working well.
I don't see my self changing to use this method on a regular basis, just playing with Puppy.