Yikes, just tried it for 1 book..and it worked :S Must've done something wrong when I tried earlier. And now for the 5th (?) time, I am going to convert my entire library and reload them on to my Kobo
Edit: Ugh, nvm. I just bulk converted the rest, and I still cannot adjust the line spacing for most. What's worse, now they have no line spacing whatsoever. I think I'm just gonna bulk convert everything with 180% minimum line height and call it a win.