Focusing on form drawing

[sly monolith]

I looked at Michael Hampton's portraiture series and gave it a shot to improve my depth control

The first one is one of my best works but still the flatness bothered me even though I added much contrast, more like the 'bryan Cranston photo realistic drawings on the internet'

The second one is what I attempted after finishing the playlist, (ignore the right eye couldn't erase it), My question is how was my form (generally on the right track?) are the steps accurate, edge choice.

Also a big one do I still use the envelope method measurements (which I used before form drawing when my drawings were flat) with the form technique or try to eyeball and good at the form proportions, cause I only used measurements for the height of the head the rest I just eyeballed

[sly monolith]

Any tips?

[high geode]

Hi!
A really good piece you been working on!
The only nitpicky that I can see is maybe bring out the eye in the shadow area (our right) a bit to the light? So it doesn't seem like the eye is sinking further into the skull (closer to ref img). Keep up the good work!

[obsidian citrus]

the neck area on the man's portrait doesnt make sense; you drew what vaguely follows the windpipe but never rendered it out or fixed it up. overall it's fine though, but you're misjudging some of the angles here and there so you might want to measure more

[sly monolith]

The more I measure (envelope technique, it becomes flat) the more I just try to draw the forms it becomes inaccurate, how do you balance that?