Even among Stampin’ Up! demonstrators there’s still some confusion about the two ‘versions’ of Stampin’ Up!’s Whisper White card stocks.
The newer Thick Whisper White card stock is 100# weight and is perfect for card bases.
Now that we have the two Whisper Whites, I’d definitely suggest using the 80# standard Whisper White (100730) that we’ve been using for years for your card layers and the thick 100# Whisper White (140272) for your card base.
Both demonstrators and customers alike asked for this and Stampin’ Up! listened. And now we have two great versions of Whisper White card stock from which to choose.
By the way, the reason the Whisper White and Very Vanilla card stocks feel like they’re a lighter weight than the colored card stocks is that the dye that’s added to the colored card stocks adds some body, giving the feel of greater weight but it’s actually only a marginal thickness.