Jay Honeck wrote:
Look at how/where the fillets join the wing and fuselage.
While a fillet at the leading edge might pose a problem with removing
the cowl, the trailing edge fillet would interfere with the flap
operation.

I've got the wing fillet mod on Atlas. It poses no problems with
either the cowling or the flaps.

I see a Knots 2U wing root fairing kit, but cannot a trailing edge
fairing kit.
To effectively do the job, you need both.
Peter Garrison had an excellent article on wing fairings in one of his
FLYING columns last year or the year before.