You don't need to take right off the edge mate. I can get like 8 ft 9/10 flat and i sorta take off from the edge, I leave myself around 5 inches or so to roll a little bit. But as Mr onzaboymarcus the third said, practice makes perfection, keep changing and tweaking up technique till you find the right one.
Just a little tip though, the preload is the most important part about gapping, I really pull the bike to my chest and jump up high on my preloads, i try and fold my rim when i preload, thats how i get the most power. Another tip, make sure your tyres at a good pressure, when preloadding, you dont wanna be rimming out, cause all the spring and power will disappear.
Hope this helps abit buddy, owt else, just ask