At patch 9.94 we can see the add in game of the 36lbs guns, the most used in the lower deck on 2nd and 1st rate vessels in history.
We must remember that no ship has ever been used in battle with the 42 lbs guns, exception for the british HMS Victory, replaced then with 32lbs at Trafalgar.
My suggest for the game is change limitation for 36lbs (usables only for class Oceàn) to be able to use in most of the currently and future 2nd and 1st rates, and add limitation about 42lbs guns only for HMS Victory.
This would be correct for a great simulator game.