HackingToolkit3DS currently can't make working CIAs since the "makerom" part is broken, it says so in the update log. It creates the CIA but never works, just google it, it's been uploaded by various people. Either find the one I uploaded with a vid on my old youtube account (comes at the top of the results if you search for "MHXX Update 1.2 English Patch V4", totally not self advertising
) or go back a few pages, someone had a link to a thread where they have a download link for that too.
As for the bigger size, it's basically because the files are translated and you need more characters to say something in English than in Japanese and because it needs a couple more files so it will work (libraries), plus it has edited logos too when the game loads, so yeah, update itself is about 22MB, while CIA with patch is about 37MB.