Check the combined size of the four fonts you embed. Perhaps they are extra large versions of Arial with a lot of fancy unicode chars?
On my computer they are just shy of 1 mB combined uncompressed. And around 500 kB compressed.
Doing the conversion ePub -> ePub with embedded fonts resulted in 1.4 mB ePub. Just as expected.
ePub -> mobi -> ePub without embedding the sizes were:
839.7 kB -> 912.0 kB -> 838.3 kB
So the file actually became smaller!
Calibre 0.9.17, Ubuntu 12.10, msttcorefonts.
Last edited by Adoby; 02-07-2013 at 10:25 AM.