I just got back some more 1971 baseball submissions from SGC with the following crossover results:

PSA 9 to SGC 96 = 4 cards
PSA 9 to SGC 88 = 1 card
PSA 8 to SGC 92 = 5 cards
PSA 8 to SGC 88 = 7 cards
PSA 8 to SGC 86 = 1 card
PSA 8 not encapsulated (miscut) = 1 card

I should add that for the most part I only send in "high end" PSA 8 cards that I carefully pre-screen with a 10 power magnifier. Interestingly, SGC will not encapsulate a miscut card even though the card has not been tampered with in any way. SGC told me that because a miscut card does not meet the minimum size of the issue they will not encapsulate.
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WrigleyField