I am sure you will have fun on Main. It is a fast track. Using my best times, I average 68 mph on JC and 86 mph on Main.
There are concrete patches in turns 1, 5 and 6. These are your friends; they are on the racing line and provide excellent grip. If you go wide in turn 6, you will end up on a huge section of tar, probably 3' X 15'. If if is hot and you end up there, keep the throttle steady and hope for the best.
The tar snakes leading to turn 3 look scary, but if you go deep they aren't an issue. There are tar snakes that you have to cross going into turn 4 (a fast turn), but shouldn't be an issue. Those leading to turn 5 are in the center of the track, at which point you should be on the right side for the left hand turn and aren't an issue unless you are hard on the brakes trying to pass someone.
Here is my shifting guide for an F4i with stock sprockets:
Turn 1 in 2nd. Still leaned over in turn 2 (a fast turn), up to 3rd.
Turn 3 in 3rd and then up to 4th.
Turn 4 in 4th and then down to 3rd.
Turn 5, 6, 7, 8, 9 in 3rd (you may feel 2nd may be more appropriate for turn 5, but you really don't need much torque until turn 6-7 by which point you are already back in the power band and if you do run turn 5 in 2nd, you will find you need to upshift in a corner)
After turn 9, I sometimes shift to 4th and back down to 3rd for turn 10.
Up to 4th-5th and sometimes 6th on the front straight and then hard braking into turn 1.
There really aren't any bumps that get my attention except the drop onto the concrete patch in turn 5. If you have a good suspension, you will hardly feel it.
Turns 3, 4, 9 and 10 are really fast. Lots of riders go down in turn 3 and you really don't want to crash in turn 4 with a concrete wall ahead.
Any off time, before the rider's meeting in the morning and after the last sessions in the afternoon, riders are welcome to either walk the track on check it out on non motorized vehicles.