Level 16 spoiler
Here is how to solve level 16 - for all of you who want to savor the challange of solving it stop reading now.
All "point references" will be refered to in "rank x file" or "row x column" form.
Starting on the bottom left face of the cube, point "1 x 4" goes right for 6 , then up for 8
Starting on the bottom left face of the cube, point "3 x 4" goes down for 1, then right for 3
Starting on the bottom left face of the cube, point "2 x 2" goes up for 3, right for 4, down for 1, right for 1, down for 1, right for 2, then up for 1
Starting on the bottom right face of the cube, point "3 X 1" goes left for 1, up for 1, left for 2, down for 3, left for 2, up for 8, and right for 3
The puzzle should be self explanatory after this position.