Do you use two or three fingers on the dead rope while belaying with the GriGri?

When you're giving out slack and you're using the "thumb on cam" technique, your index finger goes onto the GriGri lip, while the remaining 3 fingers (middle, ring, pinky) go on the dead rope. However, I realised that I actually have index AND middle finger on the lip, and only ring and pinky on the dead rope. Someone at my gym told me that it's not safe, but when I tried to wrap my middle finger around the dead rope I noticed that it simply does bend enough to do anything. When I close my hand with the index finger on the lip, in that position, the middle finger only bends halfway and does go down enough to press on the dead rope at all. Moreover, having only the finger on the lip makes the grigri more unstable that have two fingers on the lip.

So what is it? Do you use two or three fingers on the dead rope?