Nah man, nah.....There is no doubt that Henry is greater and everything but I try to imagine this fight in my head and it´s an ugly scenario for Armstrong.
I don't think Armstrong fares that badly... ... Even if ultimately he gets stopped, but I would suggest he reaches round ten, with the fight being competitive until round eight. Armstrong would hold quite an advantage in balance, strength, durability and stamina even if he was naturally smaller.
Emanuel Stewart said Hearns always had the most trouble with swarmers and south paws, but because he was so tall for his weight class i think there's a limit, Armstrong was great but he was too short for Hearns.
It would be weird fight, due to Hearns height and Armstrong's style of fighting out of crouch. Armstrong was great, higher all time than Hearns to me, but he also fought in era where low blows were excused a lot and he through many. Under standards of 1970's and later, he would be warned so often he'd be disqualified. e also liked to put head down, and keep i tin opponents stomach. Agains Hearns, he would have his head in Hearn's knee. Armstrong better pound for pound, but I can't picture how match between them would come out. Might be bad fight, although both are great.