“Reb Elyashiv says that you should put your food onto an upside-down foil container”
I don’t know of any poskim who says that this way is assur; do you?
“and if you cover it with aluminum”
Be careful, wrapping the food entirely will cause an issur of hatmana.
Sender Av, your good friend’s practices has the backing of major poskim who rule leniently; but that’s no reason to treat him the way you do.