Everyone of my BLI A unit F shells came from the factory not properly seated down on the mechanism resulting in a skewed shell and more space between the trucks and shell. Here are my findings to get them properly seated.
One way to tell if the shell is down all the way is to look at the underside. The skirts will be away from the fuel tank. This is caused by the tabs in the shell not seated in the mechanism recesses.
In the above picture, the rear tabs are seated but the front ones are not. This makes the shell higher in the front. Simply spread the shell at the skirts and remove it.
With the shell off, we can start to see why the shell isn't seated. There are plastic stops in the top of the shell that are supposed to rest on the top of the mechanism sides. In this picture, you can see where the black tape and clear foam are not in the proper position and are between the shell and the mech. The tape needs to be more forward to clear the stop.
There is a gap in the plastic stops for the tape. Simply reposition the tape so that it is in between stops. Also, while I have the tape removed, I cut the clear foam narrower so it also does not over hang the top of the mechanism sides.
<7/15/2018> I removed the part about filing the nose circuit board. There are traces that can be broken if you file too much off. I only had one that needed some filing anyway.
Once I get the shell to seat properly, the skirts are tight against the fuel tank.
I replace the front coupler with a Z scale 905 and call it a day. I altered the brightness and contrast so the trucks show up better.