How do I pass stage 2 level 10?

1) Slow down the fall rate
2) In the far left group, make the first lemming a policeman once he walks back past the fall trap, so that the other lemmings do not wander and fall left
3) In the far right group, make the first lemming a basher and let him bash towards the right. Make the second lemming (immediately behind the basher) a policeman.
4) once the basher has the tunnel through the far right column done, give him a chute and let him chute down
5) when he lands, let him build stairs over the exit so that the walks over the exit and returns instead of exiting. Then, on his way back, let him build two flights of stairs rising approx. to the middle of the wall from which he earlier chute down.
6) in the meantime, bash through all the remaining columns to bring all the lemmings together
7) when the stairs are ready, bomb out the policeman blocking the way towards the exit. Also let the very first lemming (the stairbuilder) bash a hole through the stairs over the exit, and you're done.