Picking Grip Issue

Hello,

I’m taking a look to the pickslanting primer for second time.
At this moment I’m improving my picking grip after many years using gun-trigger gripping style.

It feels good but when I’m trying to increse the speed the pick is sliding a little bit trying to return to the old style.

Is it normal?
Should I put more force on the grip?
If yes, how can I identify the right amount of force without lost the calm/rest of my hand?

Thanks in advance!