An improved headrest with adjustable connecting tubes is disclosed. The fly includes a unique abdomen. The matrix is decomposed into contiguous, non-overlapping two-dimensional cells of entries, and neural net analysis is applied to estimate reference sets of weight coefficients that provide sums with optimal matches to reference sets of values. A slave actuator having a bearing surface is at least partially disposed in the first region, and a master actuator is provided for urging the bearing surface against the transition surface to expand the mandrel against the workpiece.