Lee,
I have a 30 inch early Sterlingworth that I love. My brother in law is a Fox and L. C. Smith nut. He sold it to me. As for having a Fox guy look at it, way to many guys take a nice double down to the corner gun store and get talked into all kinds of bad ideas. They ain't making any more of these early Philly guns at prices we all could afford, so the last thing I would do is start making changes without doing my homework. The Fox is way easier than the L. C. Smiths to get the stock tension right, but it will crack if shot up with the wrong tension\fit. I'm no gunsmith, or stocker but I do love reading about the craft of the old guns and the hand work that went into each one. Not GO\NO GO type assembly. There is a rotating tapered breach lock in the foxes that made their "Bank Vault" reputation till Winchester came out with the virtually indestructable model 21. If not taken apart carefully it can be screwed up by someone not familiar with the gun.
It is easy for me to say don't touch the chokes because I reload, but I think there are soft pellet loads available that will be suitable for the gun without pounding it or the shooter. The Foxes and Parkers had different combs than most guns today and some find them "Hard Kickers" I feel mostly due to stock fit. I would not use any hard non toxic pellet in an old gun.
Also, forcing cones and chamber length as stated are way over emphasised when talking about shotgun ballistics. See Tom Rosters book and previous mentioned DGJ articles on shotgun barrel modifications for some very interesting reading about pattern and pressure MYTHS. Also note that some European Makers for pigion guns still use short cones on guns. Those guys bet thousands of dollars on a bird dropping dead in the ring and would not use a $60,000 gun that did not patten with a short shot string.
I have heard that Brilley is doing very nice work on double guns (Action\Barrel\Stock Repairs, not just screw chokes) but have not sent mine myself. Doug Turnbull in NY is THE guy for case color work. Galazan in CT has incredible stuff, but I can't afford to even look.
A copy of Mr. Macintosh's book on the Fox gun would be a good idea for anyone who owns one if you haven't read it. Tom Kidd lives in PA and I believe he can still be reached, but he does not write for DGJ any more. He is very knowledgable and would be a very good place to get info on smiths to trust.
Lee I will print two copy's of the articles on the low pressure bismuth articles and send you one if you want. I think I copied them for Steve Sutton a long time ago. They are kind of long but good reading for "Old Gun Nuts."
Are you sick of talking old foxes yet?