Supposing that Inigo has a strength of 35, and the strength cap for Barbarian is 30 (I'm just picking numbers here). If I were to reclass Inigo to a barbarian with a second seal, then later promote him to a berserker, which of the following would happen?
1: Inigo would permanently lose 5 strength.
2: Inigo would lose 5 strength, but get it back when he was promoted, but be unable to gain any stats while he was a barbarian.
3: Inigo's 5 strength, as well as any strength he gained from leveling up, would be recorded and added to his stats when he leveled up.