Well, in Oleg's games usually you are able to see
HALF of Bf-109 reticle.
Try using
"Lean to gunsight".
See in Options > Control > Views keys - for default "Shift + F1" is assigned.
Or perhaps you gunsight reticle are dimmed down (option for some planes).
Look in Options > Control > General for keys to
Increase Gunsight Illumination
Drecrease Gunsight Illumination
Some VGA, notedly notebook ones cause trouble with reticle light in Il-2:CloD, but since you see RAF ones, indicates not be the case.
Sokol1