Without reading any of that stuff I can tell you in a few words, how it works.

1. Create your beam model with the length of 1 quant in MED (don't center it, it has to start at the cetner and has to go 1 quant into x direction).
2. use c_trace with my.polygon = on (or whatever this is called now) like this:
RESULT = c_trace(vec_from.x, vec_to.x, ignore_something)
vec_set(my.x, vec_from.x);
vec_diff(temp.x,vec_to.x, vec_from.x);
vec_to_angle(my.pan, temp.x);
my.scale_x=RESULT;


something like that, or take a look nito my Star Wars code:
function FNCT_LaserBeam(fptr, tptr, AppVTX)