well i don't know how you are measuring yourselves and coming up with only 20-24" trying to measure skeletal size without bringing in muscle is hard because you have a ball and socket joint at your shoulder and the muscle surrounds it, so you have to measure in muscle and if you measure from shoulder (side lateral) to shoulder... i get 22"... So i remeasured the way you did, where it begins to slope and i get 18". But still i would assume that a football player would be even bigger than that...
Don't want you thinking i am a monster because that is far from the truth lol