here’s what the fsx autopilot section looks like… you would modify max_bank.
i am not at the pc with msfs to tell you where this is in MSFS
[autopilot]
autopilot_available = 1
use_no_default_bank = 1
use_no_default_pitch = 1
flight_director_available = 0
default_vertical_speed = 1000
autothrottle_available = 0
autothrottle_arming_required = 0
autothrottle_takeoff_ga = 1
autothrottle_max_rpm = 90
pitch_takeoff_ga = 8
default_pitch_mode =0
default_bank_mode =0
max_pitch = 10
max_pitch_acceleration = 1
max_pitch_velocity_lo_alt = 2
max_pitch_velocity_hi_alt = 1.5
max_pitch_velocity_lo_alt_breakpoint = 20000
max_pitch_velocity_hi_alt_breakpoint = 28000
max_bank= 25
max_bank_acceleration = 1.8
max_bank_velocity = 3
max_throttle_rate = 0.1