It's Maddo's record he's going for because Guinness was there at the time.
Longer claims have been made by Bird (390+'), Capes (390+'), and Alex Harvill (425')
At least Capes and Bird have footage you can watch. It's been 7 years and all you get from Harvill's jump is a panoramic multi-exposure still from ESPN. There is footage of his dirt-to-dirt record of 297' so the kid is very talented.