[kyrilliondaemon]

I know that adult winter whites will be safe with 1cm bar spacing, I don't know about 1cm bars for a younger winter white though.

And while I'm posting, if you want a purebred winter white you'll need to be really careful about where you get it. Most "winter white" breeders really sell hybrids (a cross between campbells and winter whites). I strongly suspect that does include at least one advertised in the breeder section of this forum.
(Can't name them as I suspect it'd be breaking forum rules)