Pond Liner Forming

[spawn79]

So I bought a 20mil HDPE pond liner to line the bottom of my stand as a just-in-case flood prevention measure. What I didn't realize before buying was that HDPE and LDPE are/seem to be kind of stiff and brittle. I'm a bit worried that when I try to form it to the corners it will end up too stressed and crack in the future. Of course it came all folded up too so there are already creases in the thing making it difficult to flatten out and get a good flush fit.

So here's the question. Can I use my heat gun to soften the liner a bit for the corners and creases or will that weaken the material to the point of future failure? I've never worked with HDPE or a pond liner that wasn't rubber before and google doesn't seem to be of much help in this area unfortunately.
Should I just spend the extra $$ and buy an EPDM liner instead? I don't know if that material would be more durable when forming or not. Never had to crease it before either.

Thanks for the help!

 

[Timfish]

Using a heat gun "should" help form it but it's going to be a learning experience on your part figuring out how the easiest way to fold it over itself to fit the corners.