Greg,


Sure there is a 'crossed effect', of the high-speed needle over the part-throttle fuel flow.


This effect is virtually nil at idle and at off-idle settings, but becomes more noticeable at higher throttle settings.

But since the low-speed needle is the smaller orifice at 0-~75% throttle, its effect is much greater than that of high-speed needle, at these settings.


And since the high-speed needle's position cannot be changed in flight, is is a fixed obstruction that must only be adjusted for once.

Changes made subsequently to the high-speed needle's setting, will probably be small enough not to affect the part-throttle range, but this must be checked as a matter of course.