Early on, Ithaca Gun Co. offered their Flues small bores in quite light weights --
By the mid-1920s, Ithaca had beefed up their Flues doubles quite a bit. In the 1912 through at least 1915 Ithaca catalogues they give their smallbore weights as --
16-ga 5 3/4 to 6 1/4
20-ga 5 1/4 to 5 3/4
28-ga 4 3/4 to 5 1/4
In the July 1919, Ithaca catalogue --
16-ga 5 lbs. 14 ozs. to 6 1/2
20-ga 5 1/2 to 6
28-ga 5 to 5 1/2
In the December 1, 1919, Ithaca catalogue --
16-ga 6 to 6 3/4
20-ga 5 3/4 to 6
28-ga 5 1/4 to 5 3/4
In the 1925 Ithaca catalogue --
16-ga 6 1/4 to 6 3/4
20-ga 6 to 6 1/2
28-ga 5 3/4 to 6 1/4