Honestly, I love this pic, but ahem, there is ALWAYS enough room for Shinsou

And if there isn't... then he'll make room (gaze intensifies)

Shinsou: Hey, Iida, are you sure I can't have Midoriya!

Iida: Of course you ca-- (hypnotized) ...

Shinsou: (smirks)

(But seriously, that grouping is not symmetrical; Shinsou can definitely fit!)