Buly,

Bring on the bull, my Cozy won't have sumps on the side per plans( Vance Atkinson's recomendation, he has flown his Cozy for years with a sump tank but is not vented).

Much easier to use sump tank and no fuel valves, feed from both tanks, no worry about engine out due to tank switching or selecting wrong tank. Maybe a transfer pump might be in order since everyone says the tanks won't feed the same ( could see the possibility if long lines were involved).  Intend on keeping the return lines balanced as to pressure drop (length & fittings and such). I think dual vents, one to each main tank my be okay, but am leaning toward Perry Micks valve capped vent so if feed is somehow restricted the fp can suck fuel. As John Slade can testify how those pumps suck.

 

Wendell