20 degrees from what point? Looks like those lines merge at the gunsight or forward canopy. The head (with the eyes that see) is against the headrest at the back of the cockpit. I think the current view is about right.
Take the diagram WW posted with 20 degrees. Now, keeping the lines touching the fuselage behind the cockpit, move the point where both lines connect back to be about where a human head is situated. That spreads the angle of the blindspot out MUCH wider (closer to what we have).
FOV position dictates the angle of the blind spot. I think the problem isn't the optics themselves. I think it's just a matter of not allowing the head to move enough to narrow that blindspot down a bit