I think it's up to me:
Sm-97 No data. COULD (emphasis) be the intended designation of an un-named four-engine, triple-fin, trycicle landing gear civilian transport dated from October 1943. An evolution of the SM-95 with a new fuselage.
Sm-98. No data/not assigned
Sm-99. This designation is found in the mid-war private notes of Ing. Ermanno Bazzocchi (of later Aermacchi fame) as a potential competitor of the design he was studying at that time of a two-three engines light-to-mid transport. Could have been a "fictional" designation for some sort of late transport/civilian version of the S-79 with new engines (like the ones sold post-war to Lebanese Air Force).
Sm-100. Not assigned. I personally sometime use it to designate a misterious design documented only by an unidentified model in the Agusta Museum in Cascina Costa. Evidently inspired by Miles "X" designs (particularly Miles X.2 from 1937-1938), figure it as an airplane with a fuselage with an airfoil section mated with the Sm-95 wings and engine nacelles. Actually it could be a "milesque" version of the supposed Sm-97.