I have an Aarn pack. It has stays in the back pack and each of the front packs, but it also has instructions on how to fit the pack with the help of a friend.

It does not have a framesheet, however. I wonder if the framesheet has something to do with the problem?

The temptation is to really make a noticeable bend in the stay. I found that we adjusted too far the other direction and was able to remove the stay and bend it back somewhat without a lot of duress. But the pack is clearly made to be adjusted this way, with instructions that reflect this.

Have you looked for documentation on the Coleman website? Granite Gear doesn't send their literature but you can download it from them.