Fiberglass? I don't know bout you but that sounds mighty uncomfortable to me. You ever had a fiber glass sliver or itch like crazy cause that stuff got on you.
Clear:
I'd avoid any non-paper products for nesting. Throw in some napkins instead or lightly torn pages of an old phonebook. or if there's enough bedding (and you say they have a hide box) they should be fine without. I just find that mice with something to shred spend less time looking for escape.
Fiberglass just sounds bad!