Campag4life

Both John Cobb's videos are excellent. Keep in mind Trom...reach is a function of horizontal reach AND drop. Mr. Cobb's videos did not address horizontal reach. If you drop your bars down, it is possible you may need a companion 'decrease' in reach...perhaps even a smaller bike with shorter top tube.

The points Cobb makes in the video in my experience are correct...sit bones grinding causing butt pain if riding too upright and the bars pushing back on the shoulders which can cause neck and upper back pain and raising the bars having the opposite intended benefit. But...like anything, a little medicine can be helpful and too much can create more problems than solve. For example, a 12cm drop for what he calls a B back rider is a bit extreme. Lance rides with a 80mm drop or much less than what Cobb suggested...Lance's position being almost recreational except for being stretched out...and George Hincapie as discussed in the other thread rides with a 114mm drop and he has very long arms...and less than what Cobb suggested for the average cyclist. The A back cyclist he showed had fantastic flexibility. My personal view is 2-3 inches drop or 5-10 cm of drop is good for the average cyclist but it does vary and horizontal reach is in the mix as well. A flexible average rider can endure and benefit from more. Also flexiblity and tolerance for drop can improve with more time in the saddle.
In my personal experience, you want to offset drop with saddle setback to keep the weight off the hands.

As to neck pain...visualized your riding position above with the bars pushing back through your arms putting tension into your shoulders, traps, upper back and neck. By lowering the bars, the compression goes out of your arms which actually frees up your neck...even with a lower torso position relative to the top tube. Stress can transfer however to the lower back if there isn't suitable pelvis rotation which is key as Cobb explained in his video. It is pelvis rotation that creates the aesthetically pleasing flatter back.
A final note is reading this thread, I really didn't read why many prefer a higher handlebar along with their pelvis rotated rearward as shown in the B back video with the heavier rider starting out with only 1 inch of drop or so with riser stem. In my opinion, this is because for a male, rotating the pelvis forward may be the worse of evils...sit bone pain versus perneal or pain in the nuts. To me, this is why saddle selection is critical. With a cutout or relief in the saddle, it is so much easier and more comfortable to rotate the pelvis forward into a straighter back position which allows for more drop. If you try this on a Brooks with prominent up turned nose section, it is painful for many including me.

Below is a chart for drop furnished by Dave Moulton comprised of thousands of fits over 30 years:

PS: Does anybody recognize the two white saddles that Cobb talked about in B back video?...one what he called a plus and the other a Max or maxi?