I don't trust the odd leverage loads the bar ends will create on the riser's bends. Plus in my (never-so) humble opinion it looks DORKY. I mean DORKY as in ride the short bus, wear plaid polyester pants, and have a "girlfriend in Canada" (when you live in the US far from the border) DORKY.
Those riser bars will make you forget all about the bar ends.
That plus with many bar ends the angle is way off when mounted to a riser due to the greater sweep. Some companies have a pivot mount for their bar ends that allows for some tinkering, but the space allowed between the bar and the gripped surface of the bar closes down reducing the effectiveness of one of the main positions the bar itself is there to provide.
If you want bar ends skip the riser and go to flat bar with a steeper stem to keep your ride height