I put two adult females together in a two foot cube one afternoon awhile back. The slightly larger female attacked the other in under an hour in the daytime. I separated them quite quickly as I don't want my geckos scarred up or worse for really no good reason.
Another thing to consider is that chewies bite harder and cause more damage than cresteds. Had a male this year absolutely maul the female I had him with and had to separate them. So if you do give it a go, definitely remain very vigilant.
Interested in the following (only looking for stellar stuff)
0.1's: s.taeniacuda, o.coggeri, n.levis, n.amyae, p.rangei, g.orientalis, c.angulifer, d.galeatus