Most difficult for me has been my current project - Nosen/A&A Mr. Mulligan. I have been building for almost 20 years and have been in the architectural/construction field for about the same, so the lack of instructions (2 typed pages) and only blueprints to go by didnt really affect me. What did though was the poor quality of the wood....replaced probably about 70% of the balsa and ply and added some more for strength to boot. The Nosen kits are definitely "builders kits" which makes it challenging and enjoyable for those of us who still enjoy building.