Yes the two front corners can be tricky to put in. I used a cardboard two piece "stock" replacement from a reputable vendor. The instructions said to spray a diluted vinegar solution to help form those front corners. I used Windex and it worked just fine. The trick was to use just a little and shape them as it went into place. I went a bit at a time and used the wind-lace to hold the liner up. Pushed forward a bit at a time until it met the windshield rubber. Then the fun started. I teased it under the rubber and worked it until I could get it forward no more. Then the center support, I put it in just a bit crooked and teased it into place from one side to the other. I used a plastic picnic knife to reach over the support and leaver the headliner down to the slot. Took a bit of time and some quiet breaks away from the truck. The back was easy. Do not get the head liner wet, damp is all you need. Good luck with yours. Mine still has some gaps at the sides but it looks OK at the front. The plastic knife was the best tool I could find for the job. The thin end worked the rubber and the thicker end was used to gently lever things into place. It flexed enough to keep me from putting too much pressure on any one spot. Probably saved me from tearing the liner. If you paint the back side it won't take the moisture from the Windex and get soft. So I left it just the way it came.
