I've had excellent experiences with Bob Day in California http://www.americhoke.com/ and JJ Perodeau in Oklahoma http://jjperodeau.com/ . Both pattern as they ream and make sure POI is consistent for both barrels. Mark Beasland http://www.mbabllc.com/page/page/7927803.htm opened up a French 12-65 for me based on dimensions, and it shoots great.
As to whether its a good idea, that's a decisision each gun owner needs to make about each gun. Most of the shooting I do favors open chokes; if I like a field gun well enough to hold on to, it'll likely have the chokes opened at some point unless they're open already.