Nice try, but you should use Vegas 6.0 for editing videos. Record with the replay function, NOT in-game, but don't forget to get rid of the 'replay' text flashing in the corner before starting to record you stunts. And don't forget to save your replays.
Oh, and try to use more time making and doing stunts for your stunt videos. Try to choose from your stunts, don't just use every stunt you make, and when your doing a stunt, try to find a goal for the sunt, not just random spins.
Here is a link with tutorials about SA stunting, and everything you need if you are new to the stunting world:
http://www.gtastunting.com/forums/index.php?showtopic=11682Check out the bumps tutorial, the grind tutorial an so on.
Stunt with patience, practice more and you will become great, trust me, I was worse than you when I started.