ERC will make a good ELB style bow. Just like yew, ERC sapwood makes a good back so on your next one leave the sapwood on for the back. The only benefit on adding sinew to an ELB style bow would be for protection. There are other less tedious backings that will work just as well like rawhide, silk or linen.
You can use a rounded belly but your tillering will have to be spot on. You can make it more of a deep rectangular cross section with a flatter belly.