Strain gages are applied to opposite sides of the cantilever beam member of a short tongue in such locations that the strain gages exhibit stress changes of opposite sense on movement of the short tongue compression foot occasioned by a change in tobacco rod firmness. An existing short tongue is modified by provision of a reduced section in its cantilever beam for amplifying the signal output of a strain gage supported therein. Plural pairs of strain gages may be employed for further amplification of the signal indicating compression foot movement.