i tried searching but nothing pops up

so has anyone tried stretching a polyurethane lip with a heat gun?
if so, how was it?

 

I haven't, but have represented 3 plastics companies over the last decade and know the chemistry behind it..

That said, it should be very easy to stretch (and over stretch). Simply take your time, massage it with heat, and when in the proper shape wipe it down with cold water to let it "set". Shrinkage should be minor from cooling.

I would personally make a cardboard template of the mounting area, mark it off, clamp one end down and mark the "key" areas (visually where you have lines that need to match the bumper) stretch to 1/16th" - 1/8" short being aware of those marked areas, unclamp, reform, the mount it - reheating and stretching the difference equally on both sides to make it fit right...

I ordered rep lips last week so I'll be dealing with the same thing next weekend...

 

I had to use my wife's hair drier to help bend the straight rear window spoiler to curve to the window's shape. It was rather easy actually. But ithat was a rather "small" part when compared to a lip.