If you can do 8 metres, you're going great. The word here is practice, practice, practice. Just keep concentrating on putting as much weight on one foot as the other. In the beginning it's probably wise to keep the saddle fairly close to you, as you can jab it back quickly if you think you're going to fall. (It's much easier if you press the seat against you). Then try to gently move the seat out again. It won't take you long to be able to do it as long as is comfortable. (Me, I can't ride more then 70, maybe 80 metres seat out front, before my legs collapse). I'm probably a bad advisor though, as I don't do it for freestyle, but only learned it to do seat out front jumps so my technique is probably not as good as everyone else's.