If by PCI Mac you in fact mean an Old World Mac (Beige G3 and older), the answer is:
1) less than 8GB and
2) the first partition (meaning visible volume) on the drive.
If you explicitly set the first partition to nominal 7.95GB and the second to nominal 12.05GB, you cannot go wrong without trying very hard to do so. Be sure to install OS 9 drivers if you will (and you will) wish also to be able to boot into OS 9.
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1) less than 8GB and
2) the first partition (meaning visible volume) on the drive.
If you explicitly set the first partition to nominal 7.95GB and the second to nominal 12.05GB, you cannot go wrong without trying very hard to do so. Be sure to install OS 9 drivers if you will (and you will) wish also to be able to boot into OS 9.
de