Just fill the gap. but make sure it is still sticking out a bit. Check out the pics at the top of this thread, they give a good idea of how far to push the foam in. Make sure the slit is on the underside so it won't show and look more factory.

 

I have had it like this for a year and have had no decrease in defrosting effectiveness in warm or cold weather conditions. If anything it probably increases the airflow through the vents in front of the abyss.

 

There is no effect on filling this gap, other than eliminating a poor design. Defrost works fine.

DG

 

Picked up insulation on the way to work. It will be great, but it needs a little help in being inserted. I tried doing it dry, but the insulation twisted as I moved along, thus revealing the split.

Tonight when I go home, I'll apply a little windex so it slides easily. It's going to be perfect! Thanks for the help.

DG

 

Dang it, should have done this a week ago. I lost my eyeglasses last weekend in there. Had to drive home almost blind from the beach. Kidding, my eyes aren't that bad, everything was just a little bit blurry. I'm gonna have to do this tonight. Thanks for the tip.

 

I did this last weekend with grey pipe insulation on khaki interior.....function over form!

Today, I was in a Jeep Liberty, which also has a short upper IP but no visible gap. Further investigation revealed that the large gap is there too, but they added a rubber seal to the Liberty IP to close off the chasm.

Another interoffice memo pending.....

 

So it's Friday and I'm on my way home from work. Dog tired and ready to chill. But, first things first. I stop at a local hardware and gets me some of this stuff ($1.67) and cut that sucka and install it. Fit like a charm.
Thanks to the OP for bringing this up!