Lucky you to get a hundred of Panatomic. I would (well, almost) eat my old sneakers for such a buy...
Precious as this film is, you could "sacrifice" one roll, 24 exposures (or the long ago days 20 exposures), and shoot similar images at EI 25, 20 and 16. ideally a mix of highlights and shadows. Process for the usual time plus one minute or 90 seconds, depending on subject lighting. Less for highlights, more for shadows.
You may find there will be virtually no fog. Like most slow films of that long vanished era, Panatomic preserves well.
I processed it in D76 for decades. When I shot FX, as I believe it was called then, in harsh Australian and Asian midday light, I found D76 1+1 was ideal to temper the hard shadows and bright highlights of the bush. As a second choice, I would go with (home brewed) Beutler, so second those posters who have recommended this.
Happily I still have some in bulk from early 1990s, resting in my freezer. Also a few rolls left from the '80s, and one precious roll I bought new in Asia in April 1975, complete with box and (I assume on this last part, as said box has never been opened) the original instructions. I am keeping the latter as a memento of my foolish young years, when I thought I was immortal and went everywhere and shot everything with a Nikkormat FTN and two lenses, and lived life and photography as and when it came my way.
Oh, and please post some results for us to slobber over. I will be leading the pack.