I follow the logic. But I can't find a rule.
I've heard both arguments presented here, 4 or 5 MF remaining. I've also heard the argument that the squad had expended 3/4 of it's MF, so the newly created hero also expended 3/4 of it's base 6, or 4.5 MF, leaving 1.5 plus the 2 for CX, or 3.5 MF...