Going back to your first post: You'll note from Doc Drew's and Researcher's posts that a 1 1/2 grade isn't a Field Grade. It's a couple steps up the ladder.
Good luck with your Flues. My very first American classic double was a 16ga Flues Field Grade. I only had 2 sxs back then. When #1 (a between the wars Sauer) broke down, my Flues temporarily became my bird hunting gun. The problem I had was that the stock had too much drop. When I'd mount the gun, I couldn't see the sight. As a result, I didn't hit much. But never had any mechanical issues with it. Shooting it at clay targets and calling for the bird with the gun mounted may allow you to compensate for a stock with too much drop . . . unless it's WAY off as far as fit goes.
