That is huuuuge. Technique wise, I think that taking off far away from the edge and rolling gives you a bit of momentum, also going sideways allows you to swing your hips which increases how far you gap. I don't think it looks particularly nice but if thats what you have to do to gap 9ft, then fair enough. I would much prefer do like a 6ft gap really smooth, then do it back to front wheel or something, but each to their own I suppose.