Rabbit -
I don't think its the longer stock (my new R-15 28 ga. measures right out to what my try-gun fitting with shooting session doped my measurement out to be - 14 3/4" w/ DTs.) In my case I think it the moment of inertia (MOI) syndrome - I don't shoot many lightweight smallbore guns.
My 28 ga. Citori Lightning at 28" and my 20 ga. Citori Superlight (same bbl. length) seem to travel smoothly thorugh the target arc. Likewise my Superposed 12 ga. Superlite at 26.5" bbls, but the additional weight is there because its a bigger gun physically. I think it the new (old), "starts quick, changes directions quick, then stops quick again" phenomena.
Sort of like global warming, which I wouldn't give a Tinkers' damn for theory-wise 10 years ago. Now I don't see any other logical explanation for it - rising sea levels, more hurricanes of increasing severity, etc. MOI, like global warming, is "here to stay" when adjusting to lighter guns in hand. I think I need about another 500 rounds through her before I render judgement. KBM