When installing the new 1 piece headlights, I found the gap between one of  the headlight's  lens and the body was much too large.  At first, I thought this was a manufacturing defect.  Thus I had the unit (Driver's side) returned and exchanged for another one.  When I received the second one in the same condition as the first one, I figured I had to figure out how to fix this.  The text and pictures to follow will hopefully help you achieve the same results I did. 

View from head on with lights already mounted.

You will notice in the following pictures the gap that so many of us talk about. 

Gap on the passenger side light.

Gap on the driver's side light

The problem stems from one of the screws in the back of the unit. 

Just below the headlight bulb is a screw to locate how far back (towards the body) the lens assembly sits.  (click on picture for close up)

This picture is illustrating the screw is hot glued into place.  (click on picture for detail)

More detailed pictures of the screw. 

Left side screw Notice the difference in gap between this picture and picture to right.

Right side screw Notice the difference in gap between this picture and picture to left.

Unfortunately, the normal method of turning the screw (from the front) like the others on the unit is not possible.  It turns out that the screw is turnable from the back
side.  If you look closely, you'll see that the end of the screw is hex shaped. 

Detail of screw end.  (4 mm head)

I used a nut driver (4mm size) to turn the screw inward until the gap was satisfactory.  The nut driver bit needed to be modified (turned down) so its wall thickness
was much thinner.  I did this on a belt sander.  This was because the space between the screw to be turned and the plastic wall surrounding it is very tight.

Note:  I had difficultly  adjusting one of the screws because the screw was recessed too much for even the tool to grab.  I needed to patiently turn the screw by
grabbing the threads with a  small vice grip.  I turned the screw small increments at a time.  Also, the fit was so tight, I heated the driver's tip with a propane torch.
When it was hot enough, I pushed it over the screw while it pushed (melted) the plastic around it. 

Each is a 4mm nut driver bit.  The one mounted in the tool is turned down.

End on view of the nut driver bits.  (click on picture for detail view)

I don't have after pictures at the moment.  That will come in the future.  I hope this helps.