@Sky Aisling :-
No, you're fine right there. The further outside the 'save', the better.
Some newer Puppies call this /initrd/mnt/dev_save, which is the name for this particular 'layer' in the aufs 'layering' file-system Puppies use. It's more commonly known as /mnt/home.....and is the perfect place to put stuff like this.
You CAN put it inside the Puppy sub-directory if you wish, but I would stick with the location as displayed here. This way, if you decide to add a second Puppy - and intend to use the same browsers - the profiles and cache contents can often be 'shared' between Puppies.
It's kind of like the same effect as 'sync-ing' between browsers using their built-in cloud sync tools.....except that this way, your data remains purely local, and under your control.
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BTW, with regard to your idea of putting 'restart-X' into /root/Startup.......DON'T!
I came up with the 'brilliant' idea of doing just this in an attempt to resolve something different a few years ago.....not realising that it puts the machine into a 'loop' of constantly restarting "X" over & over again. Reason being that running the contents of /root/Startup is one of the first steps after restarting "X" itself, so, y'know.....go figure!
It's NOT a good idea.
Mike.