Heh...... trust me to do it the hard way.
The rest of my solution was: when the lemmings enter the V at top-right, have the second one build to turn round while the first starts building over the gap at the end. Then just keep clicking..... making sure to save one builder for when the lemming you turned round reaches the last gap before the exit.
I'd love to know your solutions to Present 15 as well, since it sounds like they're completely different from mine!
RR99 immediately. Mine through the stairs near the end, and mine and bash under the metal while the other lemmings trap themselves in the pit on the left. Mine into the wall above the exit, then dig over the block that protrudes to the left. Release the other lemmings.... luckily you get two tries.......
Anyway......
Present 16: A Trap is a trap
7 bombers, 7 blockers, 5 builders
To save 10% of 100
Release rate 80
3 minutes
Good: kaboom! kaboom! kaboom!
Bad: ok, why the hell do you only have to save ten? I got 94 home with no difficulty at all........