Looking at Greenwood's site, it's a bit ambiguous as to whether or not he actually does the fitting. I sent a message to him asking whether he does that or just the stock building. If nothing else it looks like Mike Murphy may be an option - very close to Greenwood, both near Augusta.
I'll have to call up Champlin tomorrow and get a better picture of what the relationship between him and JJ is. The "Services" list on his page is word-for-word identical to that of JJ's own site, so I'm thinking that Champlin delegates 100% of his smithing work over to JJ. The site says they have a try gun they can use; that'd be helpful considering just about every gun on the market is too darn short for me! Champlin had a lovely W&C Scott hammergun that I called over to buy (with the intention of getting a new stock made) only to find out it'd already sold months ago and the listing had never been taken down!
One thing you could consider as an intermediate step from the fitting is stock bending and a wood extension in order to hunt and shoot the gun a bit to see how the dimensions work.
I can't seem to find pricing info for wood extensions out there - how much do they typically run? At some point it's got to start approaching the "buy once, cry once" jump up to a new stock. This gun will be used for sporting clays and the occasional skeet round. I know O/Us are theoretically better and that's what everyone my age is shooting, but I've picked up my father's weak spot for SxSs
