I think that chinatsu would have the biggest dick because it reflects her rapist personality. Himawari would have a bigger dick than sakurako because himawari usually wins the competition.
Sakurako would have a small dick to match her lackluster abilities. Ayano would have an average size dick that would only get hard when it was around kyoko. Kyoko would have an average size dick and she would use it to express herself and play pranks. Yui would have a below average dick to denote her asexuality . Akari would have the smallest dick to show her innocence and purity. Chitose would be the same size as ayano to symbolize their closeness, she would cum instead of nose bleed when she was fantasizing.