[mythtvnz] How do I record analog widescreen?

[graeme]

I have a Telstra set top box and want to record 16:9 widescreen using 
its composite input into a PVR150. 
Using the 16:9 setting in the mpeg2 recording profiles gets me 16:9 but 
the sides of the screen are still chopped off.  I know this because when 
I recorded a rugby test part of the sky watermark was missing off the 
side of the screen.

What do I have to change to get the PVR150 to correctly record  
widescreen transmissions?