My Getaway had a lot of seriously warped plastic bits. I looked for the best way to flatten them, and found this thread:
as well as some others. They all basically boiled down to two techniques:
1) Quick but scary: Put them in your oven at 225F and wait for them to just start to flatten then remove heat and press them down (but if you wait a few seconds longer to remove heat they might bubble and be ruined). There were also heater/hair dryer variations of this as well.
2) Slow but safe (but only possible in hot climates): Put them between two sheets of glass in the back of your pickup on a day when it's hotter than 100F outside and wait 2-8 hours. No tricky timing, no chance of harming them...
So the choice was basically either really risky (practice with some pieces you can afford to mess up) or safe but impractical (not everyone has a 100F day whenever they need to flatten plastic).
Well it was obvious to me that you should be able to combine these methods to get the best of both techniques. So I got two sheets of glass cut to fit in my oven. I put the (cleaned) warped plastic between the (clean) sheets of glass and let the oven heat up to 150F. After an hour or so I put a weight on top of the top sheet to press them together. An hour or so after that I turned the oven off. Once they cooled down I had pretty flat plastic (the slingshot plastic had a section that was really bent that I never got perfectly flat - I think some combination of more weight/longer time/higher temp would have fixed that, but I was happy enough with the results that I didn't pursue it).
I started experimenting with an oven temp of 120F - that went OK but I wanted to see how high I could go without any harm. I ended up going to 150F, stopped there because it was working fine and I didn't see any point in going higher. I didn't pay attention to time - put them in the oven, go to the next step about an hour later. I don't think there was any way I could have ruined the plastic at 150F.
Here are some pics:
Big Piece Before:
2. Big Before.jpg
1. Little Before.jpg
Big Piece After:
4. Little After.jpg
This could probably be optimized to go faster - you probably don't need an hour between steps, and you might be able to add weight/pressure at the start (I wanted to give the plastic room to breath/expand out as it flattened) - but I wasn't in a big hurry.
Hope this helps some of you guys who have helped me so much in the past!