I have just a quick safety tip:
Heating Kydex for too long or at too hot of a temp can cause a very toxic gas.
Rule of thumb if it starts smoking don't breath the gas!!!
I usually heat a sheet for 5-6 minutes at 300 degrees, at that heat and duration it usually comes out of the oven as pliable as a sheet of paper. Take this with a grain of salt I do not even rank as an amateur when it comes to making anything out of kydex. But I try and have done some reading on the topic.