where did you get the diy video? was it specific for your car? i can usually find something on youtube, but not for anything close to a 67 dart. i would have settled for pre-73 chrysler product; however, i am still looking.
The quality of top you purchase will also make a difference. I haven't done mine yet but do plan on doing it with a real glass rear window. That seems to be the first failure area on quality tops. On cheap tops the sail panel area seems to the the first failure area. This is based on what I have observed in Oklahoma weather.