I had a quick question. I was playing against an opponent who had brought Imperial Armory as his battlefield. This was chosen as the battlefield for the game. Late in the game I claimed the battlefield. I had a F-11D Rifle on Kylo from a Stormtrooper who had died earlier, and I overrode the rifle with Force Throw without paying a resource (since Imperial Armory reduces the cost of an upgrade by 1). My opponent and I were unsure if this was the right interaction, since it seemed pretty good. We said that it would work, but I wanted to see what you guys thought?

Seems right to me - replacing a 2 cost with a 3 cost should cost you zero when claiming that Battlefield.