When the very first Lemming falls to the ground, immediately apply him as a Blocker! Have no fear, his buddies will still walk to the right. Apply a Climber on one of them, and then, a Digger skill. Once he reaches a depth that is low enough, cease his digging by using a Builder skill on him. Then wait for him to reach the second strand of the cobweb, and repeat the same process until you arrive near the center of the cobweb. Your Lemmings must reach a place high enough to use Basher or Miner skills to get thru the web strands and reach the web rope. You will not need more than 4 Bashers or Miners, and you have plenty of them!
Once they walked the web rope, getting thru the second cobweb is even easier. You won't need anything else than Bashers or Miners. Make sure you destroy the web strands where your Lemmings won't end up in the void below. Should some of the Lemmings walk back the web rope, set up a Blocker to avoid this. You won't be able to save them on such thin ground, but even with two Blocker losses, your rate will be 10% higher than the limit.