I can't recall the source for this list, but I think it came from Eric. Note that the "classical" ships have the same base sizes as suggested in the Roman Seas Model Assembly Guide.
Roman Seas Base Sizes
Roman Scout, Hemoila & Liburnian, Carthaginian Monoreme & Bireme, Small Merchant Small Actuaria, Small "War" Actuaria, Small Saxon, Large Saxon: 5.0 x 3.0 inches
Roman & Carthaginian Trireme, Medium Veneti: 8.0 x 3.5 inches
Roman & Carthaginian Quadreme: 8.5 x 3.5 inches
Roman & Carthaginian Quinquereme, Antonian Heptares, Large Merchant, Large Actuaria, Large "War" Actuaria, Large Veneti: 9.0 x 3.5 inches
Roman Hexeres & Antonian Octaries, Novares, Deceres: 9.0 x 4.0 inches