Weren't those flat decks as well?
Yep
18' Cyclone (flat deck)had a deep entry bow which had a tendency to bite and spin.
18' Super Cyclone (flat deck)had a shallow entry and a better bottom.
18' Bonneville (bubble deck) on the same bottom. Bubble deck took 6" out of the seating area so the
19' Bonneville TR (bubble deck)came out. New bottom, strakes and drop chines, as Nick stated.
20' Bonneville Classic had a simular bottom to the TR with bigger strakes.
21 VIP Spectra bottom w/ a steeper step in the deck
That's the line up as I recall.
Sorry got a little carried away