I'm with Trie here, no major trouble seeing it as hollow when it's facing away.
There's a kinda similar scene, but more complex, towards the end of the film Victor/Victoria. Four crossdressed dancers/cabaret artists are performing facing an excited audience in a Berlin club in 1932, and several times they turn around fast in formation - and hey, presto! each shows a male face, gender opposite to the one they had before. It's some time since I saw that one but they are all female at the start and then they show male faces, actually some of those latter ones are masks, but they look very convincing, with some typical old-style "pre-war show" makeup like Joel Grey and the others in Cabaret, or even Chaplin. In reality, all of those four actors are male, crossdressing as women, though I don't think any of them has a hard full-face mask on the "woman side"
Amazing scene, and a very interesting movie (even though I think you have to make a stretch to really believe that anyone could think Julie Andrews is a genetical guy playing a woman, when she's on stage). The scene isn't on youtube, but the film does run sometimes on TCM.