Making a leather covered quilted linen cuirass

[Theodosius the Great]

Thanks, the article confirms my ideas about linen armour. The point is that it shouldn't be seen as just a 'subarmalis' for a metal armour, but as armour as such.

The idea isn't entirely implausible, IMO. But the earliest unambiguous examples of quilted, fabric armor that come to mind are the cotton shirts the Spaniards adopted from the Aztecs. And only then those shirts provided some protection against the stone age weapons they encountered. So, I'm not sure how useful a similar garment would prove in a Roman context. If a Roman was too poor to afford metalic armor I suppose a linen subarmalis was better than going Celt. Even so I can't imagine the widespread use of a subarmalis as standalone armor during the affluent age of the Late Republic and the Principate when metalic armor was in abundance and provided by the state. I'm curious what type of impression you have in mind to wear the subarmalis with. Legionary, auxiliary, marine?