18:49 

1-4 - 332
2-4 - 775 Lose 1 subpixel string on elevator duck to get good bowser
3-4 - 1129 D+R on 161 and lose a subpixel string to get good bowser
4-4 - 1521
5-4 - 1886 Lose 1 or 2 subpixels strings total on bar and elevator ducks to get a back bowser
6-4 - 2250 run off the stairs, hold D+R, and jump on 223-225 , lose a subpixel string on ducks (can lose more if you do the 223 D+R), to get a forward bowser every time. This reduced the lag you get on this frame rule from 6-8 down to 2-4 frames. Instead of frame perfect last fireball, you can also just duck under and turn back.
7-4 - 2689 Lose 1 or 2 subpixel strings on your ducks, 3 frame window to jump over podoboo and avoid damage from podoboo or bowser. Bowser is forwards every time, just like in 6-4, I didn't get any lag on this framerule.
8-2 - 2932 Lose a subpixel string on your ducks on the stairs at the beginning of the level. Fast blant gets a really fast shot with plenty of frames to spare (frame 11 jump), a slow blant gets a slower shot that still saves the framerule with a frame to spare (frame 23 jump)
8-4 - 3135 Go faster than 8-A to ensure good bowser patterns (do fast accel in turnaround). Jump the last 3 frames possible on every pattern and never worry about ducking. This tas got 8-E which is the tightest pattern on this framerule, and still had a 3 frame window, the other frames are a lot more lenient.