Tracing is good because USE_BOX uses box borders for distance(at least i think so).
But i think your code for placing object isnt exatcly right.
It should be as
Code:
vec_set(my.x, target.x);//place object at scanned point
my.z += my.min_z;//possible you can add some more quants if you vant it to not stuck in ground(if using c_move aftervards)

If my.min_z is negative just give -my.min_z;

Arrovs once will publish game