You mean like the MS1000 mod?
I know it's not exactly the same thing, but I did previously have the drivers recessed in the cups.
My impressions were not very favorable. It seemed to make the mids distant, and eliminate a lot of bass.
With that said, it did not have the distancer holes or felt that are so vital to the MS1000 mod, so please take my comments with a grain of salt.
Yes, I mean like the MS-1000 mod. I did read your post after I wrote my question and felt like that pretty much answered it. Still curious to see if the holes and felt would make any positive difference to the SennGrados. For now, I'm thinking about adding spacers and a wood cup to my SR-60es.