First of all, props to you for being out there on the track with the big 4 strokes. But, you dont need to pull off the track to let them by. Just keep to the inside or outside and let them go around you. Pulling off the track is completely unecissary.
Watching this vid, I bet you got real tired during your first race, didnt you?
Its good to have some weight in the back when going through whoops, but you dont want to be hanging off the back of the seat because then you are pulling on your arms and your arms are going to get tired. Ride using your arms as little as possible. Use your knees to pinch the tank so that you arent holding on to the bars so tight when cornering. Get a medium grip gripper seat cover and it will also help your arms from getting tired when accelerating.
Going into corners you should be using the front and rear brakes. Its just as important to use the front brakes as rear brakes because the more weight on the front tires, the better you will be able to steer. Keep in mind its always faster to rail corners than to break the rear end loose and drift around them. Im not expert, but in my years of racing this is what Ive learned.
Here is a pic of me from earlier this summer.
Like I said, Im far from a perfect rider, but I have raced many nationals.
Notice the compressed suspension on the front end. That is because while entering the turn I was applying the front brakes along with the rears to set myself up for the transition of going from 4th gear WFO to 2nd before starting the turn. The goal is to try to turn while spinning/sliding as little as possible.
On a good execution, you will maintain perfect traction and shoot out of the corner like a bullet, like so....
Here is a not so good turn, as you can see Im sliding the rear end around which means lots of spinning.
If its real hard packed, dry or real wet sliding is inevitable. Just try to limit it as much as possible. When you get some shocks you are going to notice a HUGE difference.
To summarize this, go into a turn HOT, as fast as you can, and brake HARD entering the turn, try to maintain traction without sliding too much and accelerate smoothly through the entire turn.