I think this is a good place to put him, but tbh he could be higher than this and he just has yet to prove it. A few things going for him:
1) He was stated by Mougou to be the most talented man that the Mou family has ever produced, and that includes Moubu who is on the level of the Qin 6GG or maybe even above in certain aspects.
2) Shouheikun himself said that he doesn't understand the full scope of Mouten's talent. That is an other-worldy hype statement right there lol.
3) His subordinates are fully convinced that he is already as talented as the 6GG of Qin, I understand some might question a statement like this and that's understandable, but to me this is enough to assume that he's on the same level as them when added with the other stuff.
He's got some other hype going for him too but I feel like this is enough to justify his placement here. The only reason he isn't higher is because he's young and imo hasn't proven himself to be above the others yet.