Iain Oughtred's double enders are rightfully very highly regarded and HBBR members may well be considering building one.
The Tirrik is the middle size Tern at 16'10" long, so a garage build is just about possible. The smaller tern is the Whilly tern, then Tirrik (name of the Common Tern) and the Arctic Tern at 18'3" and Ness Yawl at 19' something. The earlier version of the Tirrik was known as the Ness Boat.
So, here are some pictures and videos of sailing a Tirrik that might be helpful in judging if she might be a boat you could consider building.