Hey guys, I will be picking up one of these very soon and I need some advice first. First is the memory card....... How long will the a 4GB card last at the 720 setting? How long will the 16GB last at 720? Which speed is best to get for the best video? Now, with the mount.... Two people will be using this and I'm wondering what people think is the best mount option. I want to do the handlebar mount but seen mixed reviews about the extension arm breaking. I'm also thinking about the chest mount option...Has any tried both, what's best? I've seen a ton of videos, some are awesome but some are horrible, just wondering what everyone's opinion is?