Is there a reason (technical maybe) behind the fact that when importing an image (cover for example), the output is much bigger than it should be? I mean, 5mb is a bit much for a 300kb cover.
I’m asking out of curiosity and to know if it is a known issue (I didn’t find any topic yet) and because it’s an extra step I would gladly avoid, fiddling within the epub to replace the image.
The main point is the png cover will be much larger than a jpg cover. You could try converting if using a png to a jpg and see if this reduces the size.