World 5-S Final Jump

I'm having trouble with the final jump in world 5-S. (The one that you get full health from) I can't tell if I'm jumping too early or too late, and to make things worse, this jump occurs at the end of the level, meaning that I have to play through the whole level all over again just to get another chance. If anyone can help, I'd appreciate it. Untill then, I'll keep trying.