Complex sentence: A schooner with her dimensions would have required a certain amount of ballast to combat lateral forces against the sail, however, the "Codseeker" was not built with the customary amount of counterbalance, most likely due to the schooner's depth.
Split into simpler sentences: A schooner with her dimensions would have required a certain amount of ballast to combat lateral forces against the sail. However, the "Codseeker" was not built with the customary amount of counterbalance, most likely due to the schooner's depth.