After reading a post on gamefaqs about boosting I decided to look more into the slower approach to making my cards stronger. That approach consists of maxing the level of each fuser cards prior to fusing both cards together, this is information that I wish I had prior to fusing some cards already. Fortunately I didn't mess up many cards by fusing them without maxing their level first. The Iron Man cards I mentioned that I am preparing to fuse are both sitting at 30/30 lvl with ATK: 2310, DEF: 2440. After fusing the new Iron Man+ card has stats of ATK: 1566, DEF: 1664, the stats that carried over were ATK: +231, DEF: +244 on each card.