Shipbldr,
Mine's a Xantrex too. An XPower 1000.
Their spec page says 1000W continuous, 1200W 5min continuous. I wonder if we have the same one.
Anyhow, I finally got a reply from their tech support saying that a 14' [one way] run would work, but might just provide less clean power. And that it'd more likely be a problem for running computers and monitors than tools.
So if you used all but 18" of the 26' length, that's about a 12-12.5' run one way. So I guess I'll go for it.
When you say through the firewall, did you make a new hole?
I guess I'm going to have to pull the sill covers and the rear storage tray and explore to figure out how to get up to the cargo area.
BTW, I started to pull that driver-rear tray up and discovered that it's going to be a bitch to get it to clip back in. The plastic panel over the wheel well has so much flex that getting all the barbs in the tray that hold it on without having a way to push up on the flexy interior paneling is near impossible.