I think you need a compression tester first.
Then...answer the rest of the questions...
1. Do you have the timing advanced?
2. What elevation and temps do you ride at?
3. Are you holding it open for a long time in 6th gear (Wide Open Throttle, or WOT for short)?
All of these play a part. Your jetting and octane could be fine...however, if you're holding it WOT for a long period of time, it could be running the float bowls dry, which will lean it out...and cause detonation (and the plugs to back out)
Several factors contribute to plugs backing out from detonation.
You'll need to answer ALL of the questions, as well as get a GOOD compression tester with the same reach as the spark plug (threaded end that goes into the cylinder)
Also...you MUST do the compression test correctly. Warm the bike up, remove both plugs. (Make sure the ignition is turned off)
Thread the compression tester in, hold the throttle wide open...and keep kicking. Not 1 kick, or 5 kicks, or 10 kicks.
Keep kicking until the gauge no longer goes up. Often, this can take 15 kicks, 20 kicks or more. The first two or three kicks the gauge will jump pretty good. Then, it'll barely go up a few PSI at a time. It is CRITICAL you keep kicking until that needle doesn't move at all anymore.
I'm basically getting at don't just "kick it 10 or 15 times" and call it good. Keep on kicking until it doesn't move on the gauge, however many kicks that takes.
Then, repeat for the other side.