How to set hover pitch so that heli doesn't drop while going from pos hold to stab mode?

Hi all,
Setting up small Blade 300CFX flybar-less electric Heli. After rate tuning, its flying nicely. But it drops suddenly if i switch to stab mode from pos hold while hovering. And it starts rising if i switch to pos hold from stab mode. I am using governor mode on castle esc.

It’s kind of heavy and it hovers when my collective is at around 1800ms (+60 shows on my qx7 transmitter display).

After searching, i found that i will have to play with IM_STAB_COL settings but i need assistance please.

Another question:Would setting up notch filter help as the amplitude of vibrations in Rate Roll is not much?I am attaching pictures.