Tailplane warp fixed using Andy's water method.
Both were damaged a little (port more than stbd) by the clamps, but nothing some filling and sanding won't fix. Want to fine-tune the process though, should I need it in future.
Yeah Don, I think each method has it's merits and trouble spots. It's pretty much 'six of one, half a dozen of the other'.
In this case, the metal clamps I used cut into the plastic, even before I heated it. I decided then to use a thin metal bar clamped with same said clamps, which resulted in a nice long indentation of the bar after heating...we live and learn...