Fix for the flat foot - and it ain't arched heels, smart guy

Has anyone tried fixing the “flat foot” syndrome of old flutes by inserting something into the bottom of the bore? You’d lose the low C on your 8-key, of course, but feck the low C! I tried this just now with my recently purchased Geo. Cloos, which I haven’t foisted on my friends yet - playing along with records, though, it sounds very good for tuning, along with everything else. Putting a Sharpie (felt-tip pen) in the bottom brought up the bottom and middle D a smidge. Mmmm! I tried an early Rudall and Rose last month that was quite nasty for the low D, especially in a tune like the Plains of Boyle. Maybe this “cork at the other end” idea could be the salvation of some of these oldies - or maybe the players used them all the time and didn’t tell us! Musicians’s guild, you know. Tricks of the trade.