Bill, the Great Kilt was a great advantage to the Scottish armies of old. It was deliberately designed so that you could simply wrap yourself up in it, lie down on a bit of flattish grass, and fall asleep. The fabric wasn't inherently waterproof, but the very close weave kept the water out whilst remaining breathable. This made the Scots armies formidable, because they didn't need to carry tents etc, and a whole army could be mobilised from camp in a matter of minutes. They could also camp in a much smaller area, compared with others using tents.
In addition, in normal civilian life, brave travellers from one town to another, eg. visiting relatives, could manage a walk over the moors taking several days, and make camp at night in the same way. Obviously only a few hardy men would have done this, but it was not uncommon.
On a side note - I like your cuben fibre kilt. It looks very cool (temperature wise, and fashion wise)! But you may want a breathable strip of a different fabric around the waist, or it will cause your skin there to sweat and possibly come out in a rash. Please keep us updated on this. You might start a new fashion.