Besides derating, just for ease of use we always went for the next up on conduit size. Thhn always wants to twist depending on the length of the run. It just makes life much easier on the electrician with the the next size and the cost dif is worth it to me. Just passing on an idea.
This was a long time ago but we ran 4" conduit to a magnetic mixer in a steel mill, used a 10 ton crane to pull it around 40'. I know crazy, we used max NEC to fill the conduit and we knew we would break some conductors. I just don't like going by the recommended every since then. Even 1/2" maxed is a real pain.
