Sinister, 'Flo and Eddie', were really Howard Kaylan, and Mark Volman.

...also that they made their first appearance with Zappa as part of the masterful Chunga's Revenge, on which they are credited as (in capitals) THE PHLORESCENT LEECH AND EDDIE after a couple of roadies - either for Zappa or The Turtles (sources differ on this).

My Holy Grail of my personal Zappa Quest remains the SOFA Routine as performed by the Flo & Eddie / 200 Motels band; bits of it have surfaced here and there, and Sofa itself was featured on One Size Fits All (and Live in New York). If anyone could help me in this respect I'd be very grateful.