I logged about 50 hours (not including fabrication of the bolt-on angle pieces, which aren't included in the pre-built spars iirc) over 2 weeks to layout, drill, deburr, dimple, bolt and rivet my main spars. It was one of the most satisfying milestones for me during the project. I would definitely build them again.
I used the hammer/bolt method for most of the rivets, you'll need a powerful rivet gun or squeezer otherwise (they are relatively large diameter rivets compared to the rest of the plane). I did most of my left spar in 1 long weekend (2nd spar took a lot less time than the first one) and actually made a time-lapse video of it:
https://youtu.be/VMyZrScejgkhttp://www.rynoth.com/wordpress/waiex/2 ... pse-video/