From modeling perspective, it does not matter whether you consider a response as an effect of interest or no interest. So, just change the following two lines
-stim_times_AM2 7 ${TIMING_FREQ} 'dmBLOCK' -stim_label 7 "freq" -stim_base 7 \
-stim_times_AM2 8 ${TIMING_LENG} 'dmBLOCK' -stim_label 8 "leng" -stim_base 8 \
to
-stim_times_AM2 7 ${TIMING_FREQ} 'dmBLOCK' -stim_label 7 "freq" \
-stim_times_AM2 8 ${TIMING_LENG} 'dmBLOCK' -stim_label 8 "leng" \
Also, to avoid potential complexity, it might be better to use dmUBLOCK instead of dmBLOCK.
Gang
