I posted this on the B-Bodies website and have received one reply so far stating the glass should be "straight", which makes sense if you'll read below. Thought I'd see if others have had this problem with reproduction glass from ECS Automotive Concepts or others:

Several years ago I bought and installed a set of date coded door & quarter glass from ECS Automotive Concepts. I have never been able to adjust the door glass so it rolled up and down without exerting a lot of force and even using two hands (one on the glass) over concern of breaking the mechanism. Several people told me everything was just tight & would loosen over time. Well, it hasn't.

I was thinking today of finally turning it over to a pro to try his hand at fixing. I noticed both door glasses have bows in them that I'd never noticed before. With the windows in the up position, you can see that the glass contour doesn't follow the straight lines of the chrome strips on the cats whiskers. Laying a straight edge on the glass just above the chrome strip you can see that the glass tucks in at the very rear by a good 3/32". That seems to be forcing the glass against the whiskers several inches ahead. The passenger glass is the worse, but both door glasses have the bow.

I'm wondering if someone with a 69 B-body with original glass might lay a straight edge along the bottom of the door glass and tell me whether it's straight or not. I sold the old glass out of my car, so have nothing to compare it to right now. I'm sure it would be highly unlikely that ECS would stand behind their product this long after purchase, but if its truly out of spec I will try anyway. The glass cost $1036 then and probably hasn't gone down since.