Mart,
Thank you for defining 'fountain effect'.
Perhaps you may wish to look a little further into the subject. You may wish to consider its effect on an 'aerodynamically dirty' underbody, such as open landing gear doors.
i can't think of an aerodynamic way to make the fairings sit where they would need to be.
Perhaps a Gimbel joint at the center of the lifting-body. This will put it's 'theoretical' pitch axis at 50% of chord. Then give it a slight 'dish' shape between the four blade roots.
Dave