Running down the road in my 66 at about 65-70, windows down and the headliner starts to sag. Normally it looks very tight, but at hyway speeds it looks loose.
Yesterday I noticed the front bow collapsed (really looks bad now)
I purchase this headliner in a kit for the Chevelle, and had it proffesionally installed. They done a nice job but now 6-8 months later when I get the car on the road, it falls down.
After looking at the headliner it appears that there is no holes in it (not perverated). Is this normal?
Should it have the holes to help it breath?
thanks in advance for any help.

no one?

Pretty sure the Perf. holes are just a different look. Not to prevent anything. I don't think your year came with a perforated headliner material..
Also, your jamming pretty fast with windows down. Actually I sometimes do the same with drivers window down, 60-65. My car has the perforated material.
I still don't think that makes any differents. Just some type of air movement in your car is doing damage.

Here's my take although I am NOT a professional interior installer. But I am about to do my headliner and have surveyed the bare roof pretty closely. All the bows in my car are still in the factory installed position in my 67 because we cut the original headliner out to insure I would keep the bows in their proper place.

Sounds to me like a possible faulty installation regardless of how it looks or has looked since it was installed. A headliner shouldn't sag at any speed, windows up or down. The bow and clip system is designed to keep it in place. Those bows are held up against the roof by nylon (or plastic) clips. Re-inserting the bows into those clips can be a real bear. The center bow in a 66 & 67 is actually held in place by metal tabs bent around the bow. That one can't "sag" or be easily pulled down. Sounds like either the bows weren't inserted into the clips and tabs or the nylon clips have failed allowing the bow to rotate down. The clips prevent this. If you read the first article in this section (Headliner install write up.) it makes reference to those clips and how hard they are to work with. They are also available for replacement from several suppliers. You may be looking at professional repair help to get the bows into the clips or the clips replaced. May not be as expensive as a new install. I'd consider a different installer maybe.

When these cars were new, I drove one often at MUCH higher speeds than 70 with the windows down and never had that problem. (yes, I'm an old fart):D

thanks guys! Just got back from the shop that installed it, and they popped it back into place. One of the center clicks (as you say) came loose or was not install to begin with. They really popped it to get it back.
They said the reason it was doing that at hwy speeds is because I dont have "wind lase" installed on the sides of the roof.
My chrome/alum trim was in sad shap so I did not put it back in.
I guess that is what they are refering to.

yup