The foam core struggle is real with games that big. I measured my own copy of Eclipse twice before cutting anything, once with a plastic ruler and once with a tape measure, just to be safe. Pro tip from someone who learned the hard way: use a hot knife instead of a box cutter, it makes way cleaner cuts and your edges wont look like a beaver chewed them. Also worth checking if your box has any weird warping from humidity, I had to shave down one side of my insert cause my box was slightly bowed.

wait, so you're telling me my grandpa wasn't using that pocket for peanut butter packets?