Oregon Redleg

As a complete newb captain, I must be four kinds of stupid but I can't seem to mount cannon on any new ship I purchase... I recently ground out five passenger transports with my basic cutter on the PvE server. Those long hauls gave enough in reals to buy the Le Gros Ventre at the Kingston/Port Royal ship auction figuring I would become a trader extraordinaire. I then looked to outfit the ship with cannon and that's when the frustrations started. When I opened up the ship, the graphics told me the ship would hold 20 guns on the lower deck, either 4-9 lb guns or 12-24 lb carronades (Guns: 20, g: 4-9lb, c:12-24 lb). Off to the store to buy 6 lb medium guns. After purchasing, I again open the ship and try to select them from the warehouse. They remain greyed out and unselectable. I then buy 9 lb long guns. Same issue. 9 lb medium guns, nope. 12 lb carronades, nada. 24 lb carronades, non. Thinking it might be the ship itself, I bought the Hercules from the Steam store and bought some 18 lb guns for the lower deck. While some of the 6 lb medium guns would install on the upper deck, the bow and the stern, I could not place any guns on the middle or lower decks. Now I am out of money with a warehouse full of guns that won't install onto the ship(s). What the heck am I doing wrong? About ready to uninstall and eat the $50 I've spent up to this point... M'aider, SVP!!!