Napoleonic Series: modding leader portraits

[neonlicht]

Thought I'd try to do my own leader-portraits graphics mod for the Napoleonic games. But I'm having trouble placing the new images correctly. Even though I use the old Leaders.bmp file as a guide, I still get portraits that---once I go into the game---are badly cropped and/or have the background colour showing around the edges.

Is there a known/established method for correctly modding leader-portrait graphics?

Many thanks in advance for replies! :-)

P.S. Been using an old version of Photoshop (CS2).