Unison and Bagpipe Tunings
You may find these two tunings more useful for your "no 6+ fret" instrument than DAA or DAd; I certainly do.
Bagpipe Tuning (nominally Ccc or Ddd, a.k.a 1-8-8) is very useful for playing without a 6+ fret. It allows us to play in multiple tunings without re-tuning, just as the 6+ fret allows modern dulcimer players to play both Ionian and Mixolydian tunes without re-tuning. It can be pretty easily tuned to from DAd or DAA without changing strings, which also makes it easier to experiment with. The advantage of Bagpipe Tuning, with its deeper bass note, is that it's just a bit 'richer' in sound to my ear than Unison Tuning.
Unison Tuning (nominally ccc or ddd, a.k.a. 8-8-8 or 1-1-1) is sometimes called Galax Tuning, but "Galax" should probably be reserved for the combination of a specially designed deep body/double back instrument with that tuning. Unison, like Bagpipe, allows us without the 6+ fret to play in multiple tuning without re-tuning. The only "drawback" to Unison tuning is that you do have to replace the normally heavy gauge bass string with a light gauge string. With a 27" VSL I usually use 10 gauge strings on all three courses. If you decide you really like Unison, you'll probably want to swap out the nut and bridge as well, so the thinner bass string set better in its slots.