Don't know why it wouldn't work, we've got a guy running xB springs on an Echo. Haven't heard of it being done, but I do imagine it would make the ride softer since the xB is heavier than the Echo.
Did you notice whether the echo sets higher or lower than it did with the echo springs? Thanks, Radioman.
I think he has lowering springs and it sits a bout stock height,the ride and handling are much firmer, I would imagine echo springs on a box it would sit a little lower since they are sprung softer, and the box is heavier, your ride might be a little more compliant. don't quote me I'm just trying to think logically on this... the echo is firmer so the box would be softer.