Check out this dual PT2399 Dev Delay in action:

Detailed instructions for wiring two PT2399 dev delays in series as per the video:

-IN on pcb 1 wired as normal
-OUT on pcb 2 wired as normal
-OUT on pcb 1 wired to IN on pcb 2
-OUT/GND on pcb one wired to IN/GND on pcb two 
-Run two wires from P contact on DC jack, connect one to VCC on each delay
-Run two wires from S contact on DC jack, connect one to GND on each delay

No special modifications are required to the standard PT2399 dev board – both delays shown in the video do have the feedback mod however.

Purchase the PT2399 dev delay kit at the new Synthrotek store!