At rest ride height, the rebound spring should not be under significant compression, but without something like the adjustable SSL system, it's a lot of trial and error to get them just 'so'
It's not that hard. Here's what I did on my first +4.
Assemble the front end without dampers and without rebound springs. On level ground settle the front end. Then measure space where the rebound spring has to fit into. Then cut/grind the rebound spring to that length. Then install the rebound springs and dampers. Job done. To be fair I do have a lift which makes things easier.
Cheers
John
