On levels 13 Fun, 1 Tricky, 30 Taxing and 11 Mayhem, you can make rescuing the lemmings easier if you speed up the release rate to about 60, then make the first lemming dig at the end of the platform. The next lemming will reach him before he has tunnelled through, and providing he is right on the end of the platform, he will be low enough to survive the fall. Repeat this with the third, fifth, seventh, etc. lemmings. You can therefore afford to spread your diggers out further as long as each one digs right on the end of the overhang.