From Keith Scott, voice artist and author of The Moose That Roared: You asked for future suggestions on Capsules (Cock Robin was a fine piece). I will be totally unimaginative and request some iconic Clampetts like Coal Black or Book Revue, along with Disney's Mother Goose Goes Hollywood, or maybe a classic Avery. Although I guess it's better if the capsules are cartoons which are available on tape, if not yet on DVD, so that the short can be viewed in conjunction with your critique.
By the way, the actress who specialized as Mae West was Martha Wentworth, who did the voice for that Silly Symphony [Who Killed Cock Robin?] . The same year she had some publicity when she appeared in an episode of the West Coast radio crime thriller Calling All Cars in "The Mae West Jewel Robbery" episode. She went on to do many cartoons over the years (Mama Bear for Harman, Mamma in the Katzenjammers, tracks for Warner and UPA, all the way up to Sword in the Stone). However, I don't know if she also modelled live-action reference for Dave Hand's team or if they got a different look-alike actress to do that.
In the Disney Archives credits for Mother Goose Goes Hollywood was listed an actress named Elizabeth Talbot-Martin, identified as Garbo and Hepburn, but a 1940 radio trade publication has Sara Berner claiming the female voices in that cartoonand it is Sara.I later discovered Ms. Talbot-Martin was a stand-in for Garbo in live-action pictures, which would indicate her filming reference footage for the animators. The Archives voice credits are frustratingly both helpful and misleading: they list certain people who were only auditioning, with no real attempt at marshalling facts, and they are also rather incomplete (virtually nothing exists pre-Cock Robin).