I was just finishing up the CAD for a laser-cut can design for the t50rp driver when I came across this post... and now you've got me thinking that changing my design might be for the better!

Is the baffle in your open mod solid or porous?

Like... For example... Here is a screen cap of my vectors (closed can):

Below the main structures are the alternates for an open can:

Also... What made you choose that enclosure? Are there any physical dimensions (besides the walls of the cans which you mentioned earlier) that are particularly conducive to better audio quality?

Great post, by the way!

Wow... That is incredible.

I guess I have to look into pads a bit more.

I was looking at these for the sake of ridiculousness and comfort... but if the sound quality is changed that much, something more specific and open might just be the way.

Did you notice a significant change in clarity/imaging/sound stage between the open t50rp and the mayflower with the same pads?

I just used some enclosures I had lying around. The baffle is solid wood, without any vent or port. I am using a modded pad, though. It seems to work with the closed T50RPs too.
Recently I bought a used Mayflower T50RP, which sounded and measured horrible btw. I left the damping untouched, just applied my pad and the attached pic shows how it measures compared to my open T50.

Yellow is open T50, red is closed Mayflower. Both setups use the 'StratoPad'.

That's pretty awesome, so all that has to be done is to tame the honk at 1 KHz with some damping and install a pair of stratopads, huh?

Following the business philosophy around headphone forums you should be charging $500 for the pads alone

Is your last iteration based on the HM5 pleathers?