Wow... Tricky stuff. Difficult to reproduce everytime but after a while I've found how to do it easily Spoiler: Hint I am not going to spoil in detail but just to say that when R turns in the stairs the draggable is your friend... If you follow the move.
@Gepeto - I don't post levels where I can't consistently finish a level from start to finish every time. I took some tweaking to get to a solution where I could nail it every time. I figure it's like when someone figure out every minute mannerism to get through a level of Super Mario Bros. Spoiler: A further small hint Yes, the draggable is your friend, but it's good to recognize when your friends have lost their usefulness and might interfere with your plan. That's when it's best to put them down. A little practice gives a better feel for when it's time for the hard goodbye.
Thought this would be very easy on immediately spotting the trick required, but took a few attempts to get the timing right.
@ridgerunner - If you're looking for more of a challenge, then I suggest you give the levels parkour 1 and mystery island a try. Enjoy!
I actually found another solution for this one. Spoiler Autopilot towards the Win when R is turning around and walks by the Win platform. With the right timing, B would use R as a stepping stone and land directly in front of the Win.
Whoops, another 3rd solution without using R (but more difficult to replicate): Spoiler Autopilot directly to the grass surrounding the Win (preferably to the right side). B would land directly on it sometimes.
Tricky! But it's clear a trick is required. Timing is not difficult for me, in the sense that I do it as fast as I possibly can from the level start. If failed, restart level rather than wait for R. 
Buufff how a small level can give me a headache jajaja...after I "see" how to do it,is a question of timing...sometimes small levels are more complicated than big levels...good job