Silkies and Polish should be an ok mixed flock as both are lightweight, crested, and somewhat docile natured - provided there is plenty of room for them (no crowding).
All the crested breeds seem to be docile skittish personalities because of their blocked vision. However my Silkies free-range and there's not much fluff left around their face to obstruct their vision. Instead of fluffy crests they have porcupine spikes sticking out all around their face. I don't wash the gunk out of their crest because I like that they can see where they're going and aren't so skittish. They love to forage but pick up all sorts of spider webs and debris in their crests. Not until they get matted do I take a wet towel to their crests to clean them up.
One year my oldest Silkie went completely bald. I thought she was moulting only to discover that it was the bully Marans picking at her. That huge Marans was sneaky and she nipped and snapped at all passersby - just nasty tempered. Her new owner says she's still a snot but keeps her for the dark eggs (which really are not chocolate but just a brown!). Thank goodness my sweet little Silkie got all her head feathers grown back no thanks to the nasty Marans.
As a side note I noticed my APA Blue Wheaten Ameraucana (my avatar pic) is a gentle soul. She is not interested in flock politics and avoids conflicts at all costs. She'd rather run than fight another chicken. These girls don't seem to have a mean bone in their body. Because they are good egg layers, gentle natured, people and flock friendly, I would not keep them with Heavy LF or Dual Purpose breeds that have the tendency to be strongly assertive breeds. Because egg layers should not be stressed I would not keep the gentle Ameraucana in a Heavy LF flock but I wouldn't hesitate putting Ameraucanas around gentle Silkies or Polish. Blue Wheaten Ameraucanas are kept by OurFlyBabies.com because they will accept orphaned chicks or injured birds into their flock where other breeds are not that friendly. My Ameraucana was sweet enough as an adult to let a little Dominique chick jump on top of her, sleep on her back, or pick at her muffy cheek fluff with no annoyance at all - very rare trait as not even my gentle Silkies tolerated the chick's antics.
