There is a lot of mith about how big was kimura and how small was helio.
Taking from the photo and video helio was quite taller than kimura.
From kimura biography
"Helio was 180cm and 80kg. "
Kimura was 169 cm and weight in his entire career between 81 and 86 kilos.
He stated himself that
"Neither my height (169cm) nor weight (86kg) is outstanding.", that's while he was doing pro-judo, and is the same period of helio's fight
Kimura bio
My Judo by MASAHIKO KIMURA
If you read Helio biography it's like he was 140 lbs while Kimura was a giant of 100+ kg.
That's not true , but it's true that kimura was very very strong and trained.
But as latin stated IN MEDIO STAT VIRTUS, the right position is in the middle
Other than that it's true that Kosen judo didn't exist while maeda was in Japan, but newaza did, and Maeda was a judoka. All his previous training was tenshin shinnyo ryu as a child under Jigoro Kano (before he developed judo).
Kosen judo is a ruleset for school, and some of the technique developed for that competition, like Sankaku jime (triangle choke) were developed after Maeda left japan (Sankaku was developed by tsunetane Oda).
Maeda was a student of Tomita and other judoka that, after maeda left japan, became some of the developers of Kosen rules set.