more support for your weight going into the punch and more support for your wrist. you can and should be raising your shoulder when you punch, vertical fist or horizontal fist. its not like suddenly because your fist is hitting differently you dont need to put your shoulder into it. as far as hitting an out stretched chin the vertical straight wedges the jaw into the nerve center much better. as the nerves arnt at the tip of the chin they are right below the ear but by hitting the tip it allows the most leverage for shoving the jaw into the nerves. as well the tip of a chin is not flat but the side of a face is. the vertical punch lands vertically on the side of the face not horizontally on the tip of the chin.
A vertical fist hitting the side of the face is more often than not a HOOK. There is absolutely nothing wrong with having a vertical fist with a hook. We are talking about a straight. How often, against serious boxers, do you manage to get a straight punch to the side of their head? I get that sometimes you can cut an angle blah blah etc.. but more often than not a good boxer will be facing you at all times. You will not be hitting many people in the side of the head. Even if that argument wasn't complete bollocks on those grounds, boxing is a chaotic sport, people change the height and position of their head regularly, all of which means they are NOTHING like hitting a wall.
XAXAxaxax the boxer's wasnt skilled those days!?!?!?! WTF!! Just look willie pep for exaple also dimpsey's most fights ended in the first round by K.O. so i think there were bunch of power in his fists.
Boxers of the present day would most definitely beat boxers from Dempsey's time. You also have to take into account that dempsey used smaller gloves in his time, and had an aggressive style. Which would contribute to more KOs. You are also ignoring the fact that just because Dempsey was successful with that style, it does not in any way guarantee that this success is transferrable. Look at Prince Naseem or Ali, or Mayweather, or Roy Jones Jr. What worked for them wouldn't work for about 98% of us.
i would like to point out that the book was written in 1950 not in dempseys time and long after he had trained max baer.