Safest holders for GEM notes

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I have a question that has been lingering in my mind for a while, and I now would really like to have addressed. I guess this may be directed toward Steve at BCS, but I would love anyone else's opinions as well.

I was just reading the UNC grading on the BCS site, and am wondering if the mylar sleeves may flatten or lessen the crispness of the embossing on UNC notes, thus lowering a GEM UNC 65 up to GEM 68 to a lower grade of UNC. I know the mylar sleeves are quite tight, and I have found it quite difficult to remove some notes from these sleeves, and worried that the convenience of the tight stackability is compromising my notes.

Thanks,

Manny

This is something that I would be interested to know as well, but I'm assuming unless a note is removed from a holder after a certain period of time it would likely have to be regraded by that initial grader to truly know if the grade had gone down due to this type of storage.
I know I had a number of 1937 notes in sleeves that where laid flat for about 10 years without being touched and when they were graded those that had the original ripple and embossing still had it..but then again there was no real pressure on the stack of notes ...
I know that the harder plastic holders that were used by one grading company out west allows the note to move within the holder, but many collectors found them bulky and took up alot of space.