3D pdf text map size question

In the 3D plotting options there is an option to set the texture map size to either small (128x128), medium (256x256), large (512x512) or unlimitted.  Is there a way to make this user defined?  Like if I wanted something between large and unlimitted.

I have a plot that if I use large it comes out to about 4MB but if I use unlimitted, it comes out to over 80MB, I would like some setting in between.

Ray