I know people are concerned because Seb hasn't beefed up yet but I could've sworn he said he wasn't going to get as big as he was for CW. I don't think people should worry. He's probably going to have enough time to grow that hair out and beef up.
I remember reading about how he didn’t like how he felt at his CW weight; he had to get up all the time to pee and then eat, his energy level was lower, etc. He can get to TWS beef-level, or between TWS and CW, and I’ll be happy. :)