Hi Charles,
You can estimate the group delay of any SigmaStudio filter at a frequency of interest by plotting its phase response and approximating its derivative as shown here:
Here, the composite filter at left has its phase response plotted at right. Its group delay near 5KHz can be estimated by the slope of the phase curve around that frequency. The vertical change is about 25 radians, the horizontal is 10,000 radians per second (or 1590 Hz). The resulting group delay is T = - dy / dx = 25/10000 = 2.5 mS. Because the frequency axis is logarithmic. the group delay changes with frequency even when the phase curve appears as a straight line.
Best regards,
Bob