Tricky 28 100% using no more than 1 builder.
LOL! I have never seen such a small stair at the end of the solution.
Anyway. I have made an improvement on Xmas 91 level 1 cutting it down to 2 builders by taking the ceiling route. I tried so hard to bring it down to 1 but it looks like the direct drop trick wouldn't work.
Apart from that. I've made some results for Havoc. Some of them do look quite bad, especially 7 and 17. I need particular help on 10 and 16 though.
1: 6 builders
2: 1 climber, 1 floater, 11 builders, 2 diggers
7: 1 climbers, 2 floaters, 1 blocker, 10 builders, 2 bashers, 2 miners, 2 diggers. (Without 100%, you would only need 4 builders for any solution)
8: 1 climber, 5 builders, 4 miners, 1 digger
13: 10 builders, 1 basher, 1 miner
15: 17 builders, 1 basher, 1 digger
17: 1 blocker, 7 builders, 1 basher, 1 miner, 1 digger
18: 11 builders, 1 basher, 3 diggers