For my next grading, I'm planning to demonstrate a split-kick break, similar to the kick shown here: http://www.youtube.com/watch?v=ox46E-GNVQ8&feature=related (In case the video becomes unavailable, the technique involves a flying kick, jumping between two boards held facing each other, chambering both legs and turning the hips, performing a front- or round-house to the board on one side, and a side-kick to the board on the other, both kicks hitting simultaneously.)
I can perform the kick reasonably well, but I'm having trouble with targeting: if I look forwards, I have no trouble breaking the front board (the side the video refers to as a roundhouse), but I hit the other board off-centre and don't break with the sidekick. Same goes, in reverse, if I focus on the sidekick.
Are there any drills I can use to improve my aim on the board I'm not focusing on? Or is my focus in the wrong place? How can I ensure I break both boards every time?