Sharepoint 2013 - adding code to the master page

Question

I'm trying to add some code to a master page, either directly after the opening body tag or before the closing body tag. To do this, I'm editing the .html version of the master page. All looks good in the .html file, but Sharepoint adds a lot of extra code when the master file is generated from the .html file and my code never ends up where I need it.

Is there a way to make Sharepoint render my code where I want it, without having to directly edit .master?