Oh yeah, I didn't think about the early fun levels, the only level whose floater limitation I considered is With a Twist of Lemming please.
We all fall down works out, I just checked, with each digger, you can save 9 lemmings (space apart the first two with an RR of 80, set the RR to 99 to release a cluster of 8, set it to 1 to make things not too hectic, repeat procedure). The first one digs and the bundle of 8 plus the digger is saved. So you could save 180 lemmings on the Fun version of We all fall down.