If you are here because of that, welcome. If you are not here because of that, well welcome as well, although I do warn you that the following might strike you as a bit boring and nerdy (in out hobby, who woulda thunk it?).
As was said in the discussion, magna basing ironclad ship models is usually good enough to keep them safe in transport. The factors involved is the amount of model in contact with the metal surface, the weight of the model and the centre of gravity (the lower, the less likely the model is to topple). What follows is a few pictures of different size of ships, manufactures, and material that the model is made from. They are taken whilst the models are stuck on an metal sheet that is held at an angle to show them as they would be in transport rather than as lovely looking action shots.
First picture is of three ships from the (ex) Skytrex 'transitional' steam range, from left to right the Napoleon, Ville de Paris (converted from a sailing SOL) and Ardente (frigate). They are all long and wide enough to give enough contact between the magnabase on the bottom of the ship and the carrying surface to hold them securely. As the masts do not carry sail and the hulls are relativity solid, it gives them a low centre of gravity which means they are unlikely to topple over.
Moving on the the more 'funky' designs that make the period so interesting, we have the Tonnere, Rochambeau and Onodaga. Little top wieght and wide hulls make them very secure.
Moving into the 1880s we have the Admiral Duperre and Formidable, the models get bigger and heavier but this is compensated by the wider hulls, so again very solid and safe for transport.
A few Russian ships to illustrate some different style of ship. The Novgorod is just about all surface and super secure. The Admiral Greig is another low freeboard ship and although fairly small it still has a low centre of gravity that keeps it secure. The Knaiz Pojarski and Perventetz are a bit different as they are made from resin (from Northstar?) which makes them very light so are very secure in trasit. The only problem with them is that they are so light that I have to be careful that I pick them up from the metal by the very bottom of the base as if I was careless I might cause damage as the magnabase bond is so strong.
Last couple of models - the Rurik is the heaviest ironclad model that I own (for a cruiser she was massive) and again no problems with a secure bond.
Lastly is an illustration of what 'AC London' meant by a balk. For some smaller cruiser or gun boats, who do not have much surface in contact with the metal carrying case and / or has a high centre of gravity, it is handy to magnabase some firm foam and put a trip either side of the ship to hold it in place, like so.
So, whilst I am not saying bases are a bad thing (although I prefer the look of the game without) I can say they are not needed to keep the models safe.