he said he quoted the manual (that at the moment I don't have on me).
I've always done the same as you for cover. However, for LOS, i've done as that phrase in the manual: "Terrain blocks LOS if the major body portions of the model are completely obscured"
So, for example, if i hit the model's head with the laser (and the model itself has a standard pose, not a silly one) there's LOS.
Having to use one action to switch between out-of-LOS and behind-cover would allow dick dancing..
In fact as taking MP behind cover to break LOS was a debated but not solved issue, over here in Italy we've ruled against it.