>>528300158
This example will be enabling backup sights on VAL with PSO, and removing all aiming zoom.

Open wpn_val.ltx
In the section [wpn_val] add
>3d_zoom_factor = 100
(removes ads zoom for all val variants)

In the section [wpn_val_9x39scope] add
>second_scope_zoom_factor = 100
>second_aim_enabled = true
>second_aim_transition_time = 6.5

In the section [wpn_val_9x39scope_hud] add
>second_aim_hud_offset_pos = 0.003525,0.025830,0.007400
>second_aim_hud_offset_rot = -0.002500,0.000000,0.000000
These values were copied from 1p78 variant that has backup sights. For a weapon like that has no variants with backup sights, try a similar weapon's values and edit from there. NOTE that for me, I need to edit second_aim_hud_offset_pos to see effects ingame for backup sights, NOT _16x9 value. This is only for second aim, standard aim coordinates use _16x9.

Save wpn_val.ltx

Next, open weapon_scopes.ltx
Find the section [9x39scope]
Change 3d_zoom_factor to 100
Add
>second_scope_zoom_factor = 100
(disables fov zoom on using backup sights)
Save.

Test ingame and adjust your aiming Z coordinates if you have eye relief issues, and enjoy.