Exactly the answers I wanted, although it doesn't make my decision much easier.
Basically I can dry hop my IPA now with cascade and wait to brew the stout with centennial. Or I can skip dry hopping the IPA and just use the cascade for the stout (sweet or otherwise).
Either way, I'm not to worried about it. But I have the cascade now, in the prime zone for secondary for dry-hopping the IPA. In about five days I'll have the centennial, probably fine for bittering a stout, but a bit too late for dry-hopping an IPA. No rush to brew the sweet/American stout tho. I don't know the recipe so it could well be more of an American stout, which would be fine by me. Exact ingredients available if anyone cares enough to ask.
Just tossin' ideas around. I would like to try the dry hopping on the IPA, but if I wait to try it, I'll have to wait till after the stout, because I don't see dry-hopping as a good idea for the stout brew. Will have to wait till the brew after that if I don't dry-hop now.
I would like to have dry hopped batch one (Al's celebration clone ale) but it's too late. It came out something like an amber ale. I will elaborate more on that in the appropriate thread in about ten days.
Great answers, BTW. Great place this forum!