A method, executed by a computer, includes receiving a scan chain design comprising a plurality of parallel scan chains, each parallel scan chain comprising one or more serially connected single-bit registers, each parallel scan chain having a scan chain length. The plurality of parallel scan chains are interspersed with a plurality of stumpmuxes that enable access to the plurality of parallel scan chains and segment each parallel scan chain into a plurality of scan chain segments. The method further includes conducting a determining operation comprising determining a parallel scan chain having a longest scan chain length, and conducting a swapping operation comprising swapping scan chain segments attached to a selected stumpmux to reduce the longest scan chain length and produce an updated scan chain design. A computer system and computer product corresponding to the above method are also disclosed herein.