The reason I ask is that there is a known issue with SVG and publisher's mode. But the issue is that it puts the image at the top of the screen with space below instead of centered. The same issue exists in both Marvin 2 and 3.
I exclusively use publisher's settings unless I'm specifically testing something...why else would I spend so much time cleaning up these books?!!?
So, I'm not sure what Marvin's default settings will do, but I've never had a problem with margin's on the sides.
Are they small margins - or extreme??