I'm planning to make my own Climashield Apex 6.0oz underquilt pretty soon and I'm hoping to tap into the collective knowledge bank here. The temperature rating I'm after is around 0 C (32 F). The question I've got is, how many layers of Apex will I need?

Research I've done has indicated anything from 1-3 layers, but I'm thinking that surely 1 layer can't be enough.

Thanks in advance.