From what I've seen this is a common fit issue, the corner needs split in order
to get it to sit right, but doesn't seem to be too much on an issue the other side was the same
I used a silver sharpie to highlight the edges to help me see, Trunk gaps weren't terrible, seems to be par for the course from what I have seen, Tight at the top and bottom but a bit wide in the center
One thing I discovered is I don't own enough clamps!! But #10 tek screws work in a pinch! the only thing left to do was get the trunk floor extensions fitted.after that I pulled everything back apart not its a lot of welding and grinding of drilled spot welds and some little rust repairs before I sandblast and prime.