Hi Steve,
we've put one in each tank and ended up using it with the ECI fuel injection system on our Mattituck TMX IO-360.
Didn't decide on an engine until later in the build and wanted to keep all options open. That's also why the return lines are oversize (-6) instead of -4 (ECI) or -5 (when we were looking into the subaru options).
i wouldn't be worried about weight so much. the "biggie" is rather the required duplex fuel selector valve from andair, which is $$$ (but also great quality and the only way to go when using return lines IMHO since it avoids fuel management issues, overflow of a tank etc...)
let me know if you have further questions about the ECI integration. We're not flying yet, so no performance reports yet.
it gets you ready(er) for alternative fuels, should be safer with the use of mogas (vapour lock) as well as you're ready in case diesels ever take off down the road.
kind regards,
bernie