I try to provide some data concerning the vaults in Moroseta.
That male vault is/was lethal to can be born. The male chicks with a vault died at day 18 in the egg, so they were never born.
Here in Europe when you have a 1 day old chick with a vault you could be sure it was a female.
In the US since many years the lethal factor in male Silkies is circumvented, and now also in EU.
The fact is a vault is not accepted for Silkies in exhibitions (also not for females).
This vault came in the Silkie race because of crosses with Olandese con Ciuffo in which many years ago the same phenomenon of circumvented took place for the lethal factor in the males.
Indeed after some time this vault is not more visible and only detectable by touch.
The tought for accepting a vault is that the surface of the skull becomes bigger and so providing more place for a bigger ciuffo.
There are of course big opponents for the vault because they contain also negative aspects.
I like to see some photos of your Silkies with the vault (because I am a Silkie obsessed).
PS if you find this explanation interesting enough maybe you could translate it to Italiano for our monolingual friends.