I use 3 ratcheting tie down per side and really compress the suspension. Using only 4 would work but you could be in trouble if one lets loose. With 6 total you at least have backup. Bike in first gear, front wheel straight, kickstand and side are NOT used. I haven't trailered the Busa but on my other bikes I've hooked onto the triple tree from under the frame neck, then two hooked up in the center at a frame location and two at the grab rail in the rear. Of course never toss over the gas tank or even the seat, those straps will easily crush the tank or leave a permanent indentation in your seat.
Once secured down it'll be stable as a brick wall.
Be sure to secure the left over lengths of strap! If you don't they'll flap around in the wind and start to destroy your paint job within a few miles.
As someone mentioned, check them after a few miles, you may need to tighten things or make a few adjustments. After that check on things when you stop to refuel or eat, odds are you won't have to mess with it again for the rest of your trip.