Cannot get personal helmet to appear

I painted a car and driver suit and they were fine, but no matter what I do, I get a default helmet in the car instead of the helmet I painted.

I painted the helmet in PSD then converted it to DDS. I've used 1024x1024, 512x512, I've used DXT1 with no alpha, DXT1 with 1-bit alpha and DXT3. I've flattened the layers in the PSD, in the DDS and not flattened it at all. Nothing works -- the helmet simply will not appear.

Could someone please tell me what I'm doing wrong...

Put the dds in the GameData\Helmets\GP2SHAPE folder and then select it from the profile screen ingame.