If you're passing big bikes in the twisties, roads you should be on a track because you are not going to do it on the straights. While breaking in my still street legal 400 I did a few days on the Dragon with a bunch of friends on big sport bikes. I would intentionally stay back 30-40 feet heading into the tight stuff and still had to let up to keep from running into them mid corner. But as soon we hit a short straight they are gone. On tight roads you can't pass in the turns because of safety concerns.Not sure why so many people have “passing issues” with this bike. It may be due to me being a bit lighter than most, but I dont even need to downshift shift or tuck (lol) when passing on the highway at 6th gear and im already at 80mph (not often). And in the canyon, if in the correct gear and if youre actually faster than the dude in front of you, passing wont be an issue either. If you need the power to pass someone in the canyons, you probably need to work on your riding. My personal riding experience aside, ive seen ninja 250s & 300s/R3s smoke countless liter bikes. That applies to both 30-70mph technical twisties, to 100mph+ canyons full of sweepers. But if you actually maxed out the bikes limit and cant pass the big bikes, id say take it to the track before you inevitably lose the gamble with death.
Tl;dr you will be more than happy with the 400 imo