Where I come from, the oranges are hit-and-miss - you get very sweet oranges and horrendously sour ones, often in the same batch!. So I use San Pellegrino Limonata if I have sweet oranges and Sprite if the oranges are the mouth-puckering type. Works every time.
A little on the sweet side, but very enjoyable. Nice citrus and rum hints. We used 1/2 white and 1/2 gold rum. Was perfect on a hot evening with a spicy dinner.