Once I did, I have repeated the thing twice. You need around 36-39 seconds to finish the race. Each ballon grants you with 3 seconds of time subtraction. You need at least 13 (maybe 12, if you're perfect and lucky) to do it. If you hit the birdies, you need to have a nett positive of 13 balloons, for instance if you're hit twive, you'll need 15 ballons. Use the noraml D-Pad and not the stick and it should be easy enough. Also, luck is important as the balloons layout on the first part of race, the descending path is vital, you can get up to 5 before the big part of the race begins. Sometimes the layout is awful and the trainer gets all the ballons from the path.