Plank & Planche Leans

So I've been doing plank on my elbows (without hollow because I still don't thoroughly understand the hollow). I assume the next step is on hands with feet elevated. My question is can Planche Leans be substituted in place of planks in my FSP warmup routine?

The hollow is still confusing despite reading posts about it. Protracted-depressed, right? Chin tucked in like trying to make a double chin. Still feels weird though.

hollow is more about keeping body in a straight line, as an example if you relax your abs you will get an arched mid to lower back and that breaks the form.