You want unfused but not unlined. Soft interlining, unfused. As a note, mercer uses an unlined collar (just 2 pieces of oxford cloth sewn together). Brooks' roll is is achieved with a fused collar. So, there's more than one way to skin the cat here, but a softly lined, unfused collar with proper length collar points and spacing (whatever that may be) is what you want, I'd guess.