you can use dondo we have used it for bedding and rifles to make them more accurate I don't know how that stuff will hold up under heat I would imagine that it should do very well because you are put it is car body Fielder and it would take a lot of heat from the sun outside beside the mental so I would give it a shot to see what happens the stuff that I've used is a two component compound you want to work fairly fast it sets up pretty fast but not too fast depending on which hardener you put in it if you're needing plastic baits or something to put into it to make the cavities please let me know we will gladly send you any plastic baits that you want I'm sure Mike that you will have a ball doing it there are so many different things that you can make you may want to ask crappie seeker he has worked with this stuff and made molds maybe not the same material but he has worked with different stuff I know he's not on here a lot so you may want to shoot him A PM but I'm pretty sure that he will see this post.
bob.