Sounds like you've figured out a way to put the spring in without removing the hinge-bar/lid-mount.

In studying the manual and my car it looks as if the engineers designed this for the spring to be attached to hinge-bar/lid-mount while removed from the spring box.

Now the spring can be inserted into the box and the back pin can be installed. Next one could use hinge-bar/lid-mount to compress the spring enough to insert the front pin.

[Linked Image from 49fastback.com]