One thing I'd do is changing the sprite. I don't have much time right now, but i'll see if I can find something. one that blends better...
One thing you can try and do: add half of the ship's velocity to the particle's velocity...
define a vector at the beginning of your script:
var ship_movement[3];
and every time you c_move, set the ship_movement to the vector by which you move the ship. for instance, if you're doing:
c_move(my, temp, nullvector, ....);
then do
vec_set(ship_movement, temp);
vec_scale(ship_movement, .5);
right in front of that
then, when you call the effect, add the ship_movement to the velocity like this:
vec_add(temp, ship_movement);
effect(thruster_particles,1,my.x,temp);
does this change things at all?
you might want to try using fire2_blue.tga from easy particle 3...