That palm has been planted partially submerged for a month now. I got it at home depot, i think. I bought it as a goof and it turns out it is working pretty well. It's even getting nice , new growth. I did see your post about your plant shipment. That sucks. If you want plants that can grow emersed and petco/petsmart sells, you could always go with crypts. They will grow submerged, semi-emersed and emersed. I'll be using quite a few in my next build.
As far as coco fiber attaching, i used silicone under water in the front left, otherwise all the submerged section is titebond. On the land mass, the right side by the water feature and the hills on the left are siliconed, everything else is at least 2 coats of titebond. Hope that helps
Keep warm and safe up there in IRT territory!! When your spring hits, i'll send ya some plants