Well, this took a while to be uncovered, but... 100% is possible on Cheeky 19. =) Sorry for bumping your 98% off the record chart, Akseli... =P

Try it for yourself before watching my replay. It does require glitches, but not ones that are *too* hard to pull off, and they're all well known ones.

I also majorly improved the Cunning 4 record from 74% to 89% (to be fair, I don't think anyone had actually tried to optimize this one yet). I'm almost certain this can't be improved; I'm completely sure the left side is as optimized as possible. Using a right-side solution, the best I can get is 86%, BUT I'm not entirely certain that this one can't be improved. I don't actually have a replay for my right-side approach - I did this by working out how many bombers needed for each individual obstacle, totalling them up, then producing a replay of the most efficient solution I could find. One tip I will note for the right side if anyone wants to try it - the first two obstacles (furthest right) somewhat overlap; it takes 3 bombers for the first alone, and 2 for the second alone, but with release rate manipulation and careful placement, it's also possible to pass both obstacles with a total of 4 bombers. Replay of my successful left-side solution attached. I also attached the sketch I did to work out Cunning 4, in case anyone wants to see what I considered.