So, just to memorize. The way to go is to read the spherical coordinates (phi and theta), not the cartesian. The coordinates have to be checked against implausible values and transformed using sin and cos. Finally the orthogonal planar vectors are computed from the ensuing z component to make up the rotation component of the coil trans matrix. I think the cartesian coordinates are read as well. So what you did is right. It's just the translation component of the matrix ;-) So put both parts together and transform to neuromag and you have the entire transform.