There were several tricky elements to the build. The most difficult thing I find is the suspension and steering. It was really difficult to fit in all the required things in the width available. The first time I built the front axle it was too wide. The second time it was also too wide. The third time it was the right width, but the engine didn’t fit. The fourth time the engine fit, but it was too tall. The fifth time the engine fit, but it was too long, and the gearbox didn’t fit. It was only on the sixth go that the engine, suspension, steering and gearbox all fit in the required space.
The body came together relatively quickly. Making it removable assisted in the building process by giving me two separate pieces (the body and chassis) to work on at different times, and avoid some of the parts spaghetti that comes from building and rebuilding so many times.