[ANOTHER EDIT] About the problem in your code, you must substract everything after vec_for_vertex by my.x
Code:
vec_for_vertex(trailpos2,me,46); // vertex # for top of blade
vec_sub(trailpos2,my.x);
vec_for_vertex(trailpos1,me,28); // vertex # for bottom of blade
vec_sub(trailpos1,my.x);