I have no experience working with cuben, so someone may know better than me, but I think having it be completely no-sew will be a possible problem. Even though synthetic insulation needs less loft normally than down, it still has to have air to loft. If there are no stitches at all, then either there will be air in the quilt (most probable situation) and it won't compress well, or you will suck the air out somehow and it won't loft well.
Enlightened Quilts have to have some way of pumping air into them to allow the down to loft, and you may need something similar. Having stitching helps a bit, according to Enlightened, but may not even be enough if you want it to be a quick process at all.
As for the Apex, I have made quilts by sewing around the edges all the way. In my experience, if you don't sew the Apex around all the corners, it has a tendency to move around a bit on you. It probably won't rip apart, but you will be able to see into the quilt and see it not reach the edges everywhere at times.
Also, I haven't used a two person quilt or seen specs for them, but is 60" wide enough? I like my quilts to be at least 48" wide for me alone. I think that at 60" you and your partner would be stuck right next to each other and not be able to move much.
I wrote a guide for an Apex quilt that may only be helpful for you in small bits if you decide to go the no-sew path.
Hope this all helps.