I still disagree about proportion, but yes it is " his model" so try not see it as critique, more as guidelines, based on mistakes I used to make and the biggest mistake is to think that you can do it out of the top of your head without using any guidelines to start from, even Rembrandt , van Gogh and numerous other artists used tricks ( think pencil on a cord perspective lines)to check up on their " models".
Below is a quick mark up I just made don't look at the angle of the shoulders or the ugly grey muck I tried to pass off as painting.

I'd say do what you want with it I hope it's usefull