This experimental study analyses the influence of various turbulence-grid configurations on Klebanoff modes/streaks developing in a laminar flat-plate boundary layer in a water channel. Grids were designed according to common recommendations to ensure homogeneous free-stream turbulence (FST), which typically induces meandering Klebanoff modes. In a previous study, the authors have shown that the Klebanoff modes do not meander for all grid configurations, a behaviour caused by e.g. small grid imperfections or by unfavourably chosen positions of the wall-normal bars of some grids. The present study focuses on a different Reynolds number and additional measurement positions inside the flat plate’s boundary layer. It is also shown that the transition with isolated cylindrical roughness is strongly influenced by oncoming steady streaks through improperly generated ‘FST’, requiring future FST studies to document the Klebanoff mode’s meandering behaviour.