We have 4 banties (1 silver seabrite, 1 silkie, and 2 mili fleur) in with 16 standard size birds (15 hens, and the biggest rooster you have ever seen) they get along just fine. lots of the time its the banties picking on the big girls.
we raised ours togother in batches, the mili fleur were raised from chicks with a batch of standards so they all knew each other from the start when they were about the same size. the silkie was raised at the same time as some leg horns, again from chicks. when it came time to introduce them, we placed a tractor in the coops run so they could all see each other but not get to each other. after about a week of being togother at night time when the hens were alread up on the roosts for the night we slipped the younger birds into the coop. no problem!