Randy, Sounds like you have 'stored' the spider and other body parts in an unsupported or unnatural position at some time where the ambient temp was higher than when the body parts were manufactured and they have taken a 'set' in this 'new' shape. I know builders of composite aircraft often 'bake' their parts to a temp higher than its ever likely to experience to avoid problems later. I think Rutan & co initially painted the fresh parts with water based blackboard paint and set them outside in the midday sun @ mojave while still jigged in the correct position/shape to effectively bake them at an elevated temp. While your 'warming' the effected area helps to temporarily bring it back to shape the distortion / tension will actually spread further thru the part than you can visualise as the heat that allowed this distortion would probably have been applied to the whole car etc, unless it was from say a skylight or other localised source, so in the next day or so when the temp climbs it may be enough for things to relax and move again. Talk to Frans f/glass guy to confer with him on this though,- I can see me getting in a load of trouble with both you & Fran if I tell you how I would deal with it
You really need to know the properties etc of the resin system & any foam etc that have been used to decide on how much heat to use.