Hmmm, you are in a place we have all been. Nothing more frustrating than insufficient edge distance.
Here's my take, you can take it or leave it. You need 2D to prevent cracking and deformation of the mating metals. Okay, we all know that. But, sometimes you just gotta move on. The ribs are not the most important structural element on the plane. If it's slightly less than 2D I would let go. Oh, I hear the gasping from the readers. But I can't tell you how many times I have seen sheetmetal repairs become complete hack jobs, because the person tried to "fix" one bad rivet or marginal edge distance. I shot a million rivets before my RV, I have screwed up my share of rivets. Unless they are REALLY ulgy, I know better than to try to fix them. I witnessed a situation at Boeing where a guy put a rivet in a tooling hole. 1/4 diameter rivet. No Problem. Except the inspector didn't like it. They drilled it out and then the tool to mount the door didn't fill just right. So they had to install a freeze plug, which got screwed up 2 or 3 times. In the end they had to change the entire fuselage frame at about 400 man hours and a ton of work.