I would go with the installer recommendations. The pool company is in the "sales" business. As long as your installer is one that can build you a good uniform cove out of sand, then you should be good. Does he guarantee his work? The sales pitch for a foam cove is that it will not wash away like sand when wet. I beg to differ. I had alot of trouble with my foam cove. We got a good afternoon thunderstorm mid build and the cove got wet after we had laid the liner, but before we hooked up our shop vac and started the water. Only thing that could have caused this was water getting under the wall track, or through the skimmer opening (at this point we did not have any dirt around the bottom of the pool. Once the sticky is wet, it's wasted. We pulled ours and built a cove out of sand because I didn't want the cove to shift under our liner. I know the weight of a lot of water would seem to hold the cove in place, but where there is an inch, and the way my luck went with the build, it would have shifted and ended up out of place. Foam coves haven't been around for forever and most pool company instructions recommend a sand cove. We have been fine with a sand cove and on our seconed season.