Try using a shop vac to suck the liner into place before you add water?
That's how I did my unibead liner and it worked extremely well. It's so much easier than using water to get everything into place, you should be able to determine if the liner seems to fit right before you proceed with water. You may need to add more sand to raise the floor a bit more as well as the cove. Another option would be to add a layer of XPS foam sheeting instead of sand, I sure wish I had!
A big shop vac with lots of air flow works best, slide the hose in through the skimmer hole into the space between the wall and liner, tape cardboard over the remaining skimmer and return hole. I used a soft broom to shift the liner around and had almost zero wrinkles when done. The vac had my liner pulled almost tight to the walls all the way down to the foam cove before I ever added a drop of water.
If you haven't done this check out some of the videos on youtube. I understood the principle, I used to do this years ago when I put liners in large fiberglass boxes but I was pretty skeptical everything was sealed well enough on a pool. I was surprised how well it worked.
