Never raced bents, but about 10 yrs ago in Wash DC I joined a ride with 8-9 bents, one of which was a faired Tour Easy Ti. I was on my Rotator Pursuit and found I
could not stay behind the faired Tour Easy, no draft at all, like it wasn't there. OTOH on a DF I could get some reasonable draft behind a friend on a Bacchetta Ti.
When I was riding the Rotator with a fairing, the fairing was equivalent to sitting in behind a DF rider, ie I noticed no difference in effort when sitting in behind a
DF or riding along side the DF. The fairing was ultimately removed to ease transport of the bike and because of its disadvantage in my hilly terrain locally. It added
about 3# to the bike.