Yes, you can get quite a few under those. However - they don't usually try to go broody on rocks.. which Silkies will. If you need a broody Silkie - leave the eggs in the nest. OR put golf balls in there. I just heard somewhere that they were originally created to brood partridges for the Emperors... its bred into them!
I would have Silkie eggs.. but all my Silkies went broody - only have one Frizzle girl who isn't...
Oh, that's fascinating! I didn't know that