Congrats on the results you have obtained. I too have been managing to get PSA cards into equal or greater holders at SGC but I see far too many cards that are BADLY overgraded. In fact, I just purchased two PSA 8 cards from the 53 Bowman Black & White Set. Fortunately, the seller is an upstanding guy and is letting me return them.
Here is an excerpt from my note to the seller:
Unfortunately, I will just have to go and try and resell these as they are the among the worst PSA 8's I've seen. For starters, I know that you mentioned in your ad that the reverse of both cards were clean yet there are slight stains on the upper back of both cards (more noticeable on Mizell) and the Mizell stain bleeds through to the front (top border middle).
In addition, all 4 corners of the Gernert card are touched and this is to the naked eye and there is a small circular indentation to the left of his ear.
Going back to the Mizell there is a small indentation right above his left shoulder with what appears to be an ever so small nick in the body of the card and even a 1/4" paper wrinkle about an inch in from the bottom left border in the portion of the card this is in shadow.
While I know that you are personally not responsible for grading the cards, these are not among PSA's finest for sure.
So yes STMF, I do believe that real nice cards can be found in PSA holders. As such I continue to buy them and then really scrutinize them. I know that with the stuff I am buying, I can likely resell it at close to what I paid and am willing to take the risk. I seem to have better luck with BVG than PSA and most folks bash the heck out of them. However, at the end of the day, SGC cards are more consistent.
Can't wait to see the Koufax scan!