Re:58 Harrier residual thrust?
Assume the air flowing into the (big) intake is all redirected down. There is a net forward net change of momentum to the air, just as slowing in a supersonic intake or a jetpipe, and thus there's a rearward reaction force on the aircraft. To hover a harrier without going backwards then the nozzles should have to point slightly to the rear.
I looked for images of hovering harriers after composing the paragraph, but when you get good side-on pictures, the big pylon hides the nozzles. There's also the issue of how much fine control is carried out by the little attitude control bleed jets.