my understanding was around 6'5" was avg for belters. Miller was, and Naomi was slightly shorter.
Avasarala is listed at 5'5" in real life, so i don't think the OPA guy was that much over 6'5"
anyway, found this from Ty Franck (1/2 of James S. A. Corey)
Casting Lessons, or Why Not All Belters...