I did a Havoc build article for the Winter 2018 edition of JPO's Contrails, if you happen to have a copy laying around. Like others have said, it's an "ARF" but there are still a few nice-to-know tips and suggestions. Specifically (and if they haven't changed anything since then), the main gear mounts need to be beefed up. FWIW, I love the way mine flies.
Craig