When last we saw a Tachyon XC helmet cam it was clinging futilely onto the side of another, stuck together so that the footage coming from the two could be combined to create 3D -- something GoPro is now trying to do much more expensively. We weren't particularly convinced at the time, largely in part because the resolution of each of those XC cameras was only VGA. Now there's an HD model we've been given to try, and while we've happily ditched the Siamese action to go solo this time, some issues remain here that keep us f
