used both repo and originals. If your using repos in white be aware that they are mounted to a black backing which can cause issues or at least an attempt to fix the problem.
Allot of the time I think the problems with sagging come from the fact that people attempt to install them after the rear window is installed, without the material being tucked under the lip then tend to sag allot. Reproductions often do not have enough material - had to glue additional material to them on the last 69-70 I did. Worked find - just extra work