Nero Vision menu problem

I'm using Nero Vision 5 which is part of the Nero 8 suite. When
burning files to DVD, I like to choose my own jpg pic from hard-drive
rather than use a Nero template. I just use the 'custom' pic option
and select from a pic file.
Problem is, where my Nero 6 used to automatically shrink or expand the
chosen jpg image to fit the menu page, Nero 8 often shows just a small
section of the JPG. There's a slide-control to move the image
sideways, but I can't find any way to scale the size. Is there a
solution? Or to tackle it another way, is there a perfect size I
should resize images to before importing into Nero 8? I've scoured the
manual and can't find any solution. Help please....