I put this in a different thread which is here....
https://www.mobileread.com/forums/showthread.php?t=86445
It describes my method for formating both Kobo and other EPUBs with Calibre to get full justification and also gets around the font issue. I prefer it to the standard Kobo format as it doesn't have such large margins on each page.
Cheers
John in Sunny Carnarvon - Western Australia