Hi Kevin,
You can find the equations I used in 3ddelay in these two papers:
• Saad, Z. S., E. A. DeYoe and K. M. Ropella (2003). “Estimation of FMRI Response Delays.” Neuroimage: 18 (2): 494-504
• Saad, Z. S., K. M. Ropella, R. W. Cox and E. A. DeYoe (2001). “Analysis and use of FMRI response delays.” Human Brain Mapping: 13:74-93, 2001.
cheers,
-ziad