The simplest option could be to elongate the holes in the plastic tray to allow it to flatten out. Might have to clip the sides of a penny washer to allow it to remain inside the indentation.
I agree.
My OCD tell's me that I would just like to drop the tray and then first measure and record the hole pitches measurements in the body shell.
Secondly, apply some hot air to the under tray, just to see if it returns it's once natural factory moulded shape.
If it does, now compare the measurements of the hole pitches in both items.
Maybe even lay the plastic under tray on a flat surface on the floor, with long sheet of plain paper ( wall paper would do ) under the tray and then transfer the hole pitches onto the paper.
Now compare these figures on the tracing, to the hole pitches on the body shell.
This could quickly show which hole pitches are causing the distortion / bulge in the tray when trying to install ALL of the fastens.
This may indicate if slotting the holes would then allow achieving all of the fastens, with out distorting the tray.
I am think along the same lines of "slotting" the holes in the tray, to then achieve the pick up points in the shell correctly.
My guess would be, that some ( if not all of the holes ) in the rear of tray, would benefit from slotting.
