Beachbumbob:  I do not have a Model 1896 Krag or an 1896 side-plate, in my collection, to allow parts comparison.  In "The Krag Rifle Story", by Franklin B. Mallory, he states the tenon thickness increased .02" on the 1898 side-plate.  (The tenon is the tongue, on the front edge of the side-plate, which inserts into the front of the left side receiver opening).  On page 203, Mallory shows side views of 1892 and 1892 side-plates.  There seem to be several subtle differences in shape.  It is surprising if an unaltered 1898 plate will fit on your 1896 receiver.  It should bind and fail to fit close against the action with out being forced.  Is it possible some metal was removed from the inner receiver wall where the tenon 'hooks'?