These plan were fantastic! Sorry for the messy picture!
As I live in Sweden I had to convert all measurements to metric. I also couldn't get hold of cedar boards easily so I went with regular treated construction pine. The pine boards are 45 mm by 95 mm, so I adjusted acording to that as well. The downside with using fresh treated pine is the extreme weight of the wood. It's also probably going to shrink a fair bit.
We live in a chain house, so it wasn't possible for me to build the sofa in place. Instead I hade to build it at my parents place. So I modified the plans a little to be able to build the sofa in pieces and transport the whole thing in my car. The sides are bolted to the base with carriage bolts and the back rest is bolted to the sides using hex wood screws.
To make the joints a bit sturdier I opted to use two 10mm wooden dowels and glue in every joint. I also didn't want any screw heads showing. So I used decking screws and screwed them in at an angle as hidden as possible.
Will probably sand all the rough edges in a few days and will be making a matching table later on.
As it's late in the store season (Ikea didn't have any good cushions in the store) we opted to go with rugs instead of cushions.