Thanks a lot guys. MalVeauX...greatly appreciate the advice and really all the great advice you provide on this forum.
You have taught me a lot.
I just picked up some new DT-990 Premium 600 ohm which as you well know are somewhat renowned for their comfort as well as slightly embellished sound signature which work well for my aging ears. Out of the box, they just aren't as comfortable to me as say my Senn PX100 II...now that I have had a chance to spend more time with them. But that has changed a bit per my tweaks below.
I am an engineer and design is my thing. You guys have taught me a lot about sound. I understand pressure, leverage, stress etc. I will tell you what I have done so far. I have bent the headband on my DT-990 Premiums...Premium model as you know already doesn't have stout clamp pressure...part of my calculus for getting them. As I was self diagnosing about how the pad pressure was bugging me...I determined that the pressure was along my jaw and under my earlobe...perhaps exacerbated by slightly large ears...much not grotesquely so. :) All this stuff is individual as you know...I too wear glasses at the computer which is another contributing factor. So how the pad draped along my jawline and behind my ear at the bottom was discovered to be my major pressure point. Of course with my background, a myriad of different permutations came to mind...including assymetric ear pads etc. Upon removing the pads and studying the design a bit, I stumbled on a trick to bias the ratio of ear pad pressure top to bottom. To be a bit more nuanced, by reducing the headband clamp pressure, now the pressure of the pad was reduced at the temple...but the pad by the weight of each ear cup was causing the cup to rotate and still apply a bit too much pressure along the bottom edge of the ear pads. This somewhat highlights the possible dynamic that a strong headband clamp maybe more comfortable because it evens out pad pressure more uniformly top to bottom. By shimming with some cloth between the base of the fork up top and the top of the cup..this freezes the hinge of each cup such that they can't just fall..aka rotate down into my jawline. Now I can tolerate sustained listening intervals without discomfort. Not elegant...but effective. I only wished freezing the hinge on both sides of L & R cup could be achieved by design. It could of course with some mechanical modding. This way each of us could tune the pressure of each ear cup top to bottom. Sorry to be pedantic but wanted to share this tip if others love these headphones but are getting a bit too much pad pressure along the bottom when relaxing headband pressure..
Lastly, I am slightly less concerned about clamping pressure you mention as it relates to SQ. I am a bit more focused on comfort as to me even with light pad pressure, these headphones sound outstanding.