I just got a 7.720 on level 3 by landing right on top of the first 4 armed spinny thing and shooting across the rest of the map, can't recreate it reliably yet though.

On level 4, If you jump right into the bottom of the large physics applied square, then you'll pop straight up, if you hold right and don't jump you'll bounce off the far end of the hole and get to the finish, very reliably gets me around 14 second times.

In the minecart level, I theorize that one could corner bounce off the back of the first minecart right as it falls, then roll forwards off the front lip of the second one, skipping the travel time of the second minecart.

That's all I've found for now, rest use either your WR strat or no strat