I've read the horror stories too. I originally looked for the cheapest (non-race weight) fiberglass parts I could get because my budget was so limited. I got REALLY lucky that the Barracuda fenders were made by STINGER FIBERGLASS (AAR). I had called some of the outlets and asked questions about quality, etc... and was always assured that parts would fit great. After more research I found lots of complaints customers had made though. I don't know if there is another company out there that has a better reputation than STINGER. Their parts may still need some tweaking to get them to gap properly but most people expect that with fiberglass.
Whenever I tell people that my front end is all fiberglass they're surprised. Unless you look at the inside of the panels it's hard to tell. One other giveaway is the lip on the fenderwells. It's wider than factory. My hood (that was made by another manufacturer) isn't up to the same standard. Although it's pretty good - the bottom wasn't finished very nicely and seems almost as flimsy as a race-weight part. I re-glassed the bottom to give it a smoother look and that may have added some more strength into it.
The fiberglass fenders I picked up at a swap meet (for our '68 Charger) were made by VFN. I have to say that they seem pretty nice too. The fit is good and they seem to be as well made as the parts from STINGER. I'm not as familiar with VFN though.
I didn't see Duster fenders listed on either of the two companies' websites but I'd call to see if they do make them if you're interested. At the time I ordered the parts for the Barracuda they didn't show all of those parts online.