It looks like I'll be able to butcher the RS-232 shifter cable that came with the Turtle to adjust line levels between it and the Butterfly. Rather than use the DIN connector, I'll just remove the inline shifter board from the cable and hook it up to the Cargo connector (DB25). (Picture coming soon.)
Now, about that DB25... I am ordering this to provide an easy breakout to standard header pins.
So, I'll be waiting for USPS snail mail to arrive (this week?).