Again, I have a pair and I am happy with them and would buy them again if needed.
Will they scratch? Yes. I have one minor scratch after 8 years and I run the car about 2000 - 3500 miles per summer. Most of the time they are off but they are on and off a lot. They do have the tiny swirl marks from cleaning and wiping down just like you see in a black paint job but that doesn't bother me at all.
Can they break or crack like my old glass tops did? No way.
Do they leak? I thought all C-3 T tops leaked. 
Are they noisy? Aren't all C-3's?
I believe they take old frames and rebuild them with new weatherstripping.
You can add or remove shims under the latches to get them to set properly. I use these tops on both my '78's and they fit fine.
If a car is not going to be judged and you don't want to worry about expensive glass I think acrylic gives you a good bang for the buck. And I love the weight difference.
Too bad you would have to pay shipping both ways if you send cores in.
Jeff

Can't send pics he HAD a set and he replaced them with real glass. The 1/8 higher then body is how they are suppose to fit. I have the original sun visor sleeve with the warning instructions not to push down on top it is 1/8 inch higher.
Consider how often you have the tops on. How original is the rest of car. Do you plan on having the car judged. Will affect the resale value if you plan on selling it.