As concerns ^77655, what I would actually like to know is if you think Anthony Perkins is the young man in 1:09-1:17 [url="https://www.youtube.com/watch?v=xWHYmNrAFlI"]. To me, it looks like a stand-in and that they cut Perkins in at 1:20.
Yeah I re-read your question and wondered why I didn't address that specific time interval like you asked in the original question. Huh, weird.
Anyway, I watched that part again. As soon as he walks through the door, it doesn't look much like him-I agree with you there. I have a couple of problems with that theory though.
One, when he is accosted from behind and the wig is falling off, the face the actor makes is one that I could only imagine being made by Anthony Perkins. It just looks like him.
And two, I can't help wondering why they would have brought someone else in to act what amounts to about a ten second clip. The next shot is obviously him, and as far as I've read Anthony wasn't under any time constraints during the making of the movie (unlike Janet Leigh). It just doesn't make sense to have someone else stand in for ten seconds when they could have just used Anthony. I agree that the shot at 1:09 doesn't look much like him, but I can't understand why it wouldn't be.
Random trivia: In researching this question, I learned that Anthony Perkins wasn't in the shower scene at all, because he had such a recognizable silhouette.