Reviving this thread because it was helpful and I just wanted to add my technique to the multitude of techniques on here.

I didn't see the reason that glass needed to be used for the oven technique, other than needing to see the plastic. From what I gathered nobody had any shrinkage (insert jokes) problems or other issues with their plastics that required constantly visualizing there plastic in the oven. My Stars manta ray plastics were too big for the pyrex techinique (that worked well btw for the small bits) so I just used 2 cookie sheets and parchment paper (not wax paper as noted in another thread). I set the temp at 170, sandwiched the plastics (upside down cookie, parchment, plastics, parchment, right side up cookie, Le Creuset dutch oven pot for weight) and set the timer for 45 minutes. The dutch oven (again insert joke) is basically the same weight as a engine block so that helped a bit I suspect. One small curve still remaining on the end of one of the manta ray plastics but otherwise success without loss of paint or other problems.

Interestingly as I was cleaning the plastics before the process one of the plastics sat in a pool of water for just a few seconds and paint flaked off. Water was the last cleaning product that I would have thought would wreck the print on the plastics so don't let your plastics soak even in a small amount of water.