make a model of the top row of your icicles and a model of the rest of your icicles.
So for the example below - top row is 1,6,9,13,15,20,23,27
and rest is 2,3,4,5,7,8,10,11,12,14,16,17,18,19,21,22,24,25,26,28
1 6 9 13 15 20 23 27
2 7 10 14 16 21 24 28
3 8 11 17 22 25
4 12 18 26
5 19