I got curious on the guns of the period of this galleon, after you started building it. The Portuguese and Spanish galleons must have been quite similar as it might have been the weapons onboard. I have recently read a book about an artillery fortress (Torre de S. Sebastião de caparica) on the side of Tagus where I live and about the king that ordered its construction, D. João the 2nd in 1481.
There are writen records of the king ordering the purchase of "heavy built" (my own expression) ships in France, suitable to test artillery onboard. And there are also writen documents stating fire tests (I'm not sure of the right term for direct fire in oposition to arch fire like a bombard or a modern mortar), on the Coast of Setúbal. Fire tests to study how to install guns onboard ships, calibers, range and all matters concerning firing at sea level (literally).
In this Museu Militar where I took the shots there are a lot of canons, most of them quite heavy. I think I have to pay a visit to Marine Museum to check how it looked the gun carriage of this period.