Side-loaded font bold-italic problem

Hi

I use Kobo Glo v2.8.1 with Kobo Pacher v 0.7

I use three side-loaded fonts. Charis Sil modified (published by JSWolf) is without defect and displays like it should. Dejavu-eink (published by Katsunami) is excellent but displays a bold font instead of italic. The reason? I look for it

Then there is Linux Libertine-O (an open-type font). I tried to embolden it using font forge following Katsunami advices and I obtained a 1.8MB monster much too dark with only a +60. I still have to perfect the technique.

However I had much better results in another way. The Patcher allows you to give Genius properties to your side-loaded fonts and so, I made it just a little bolder. The result is really extremely good for the Regular font. However, I must face the same defect as for Dejavu-eink, it displays italics like bold characters.

Edit: Linux Libertine-O was displayed just fine (I mean italics were just italics) before any modification from me.

So my question is: is there a general cure for the mistaken bold display instead of italic?