@GeoffR: putting other images in the same file of the cover it's a nice idea but it doesn't solve the problem for images in the following chapters.
@Anak: i tried one time to create a single file with only the image wrapped in the svg code but it didn't work and i lost the chapter information for the following part.
maybe if i use the <p> tag and a simple "add image" with images already at the right height...
i'll try it tomorrow and see if it works.
everyone, thx for the help.