After building my Deep Blue Delay I wondered if I could mod it to have tails and I found out that its easy to do with Mark's layout. Just adding a new cut, moving a cap and moving one leg of a resistor. This and using a daughter board with an analog FET switch that cuts out the input to the PT2399 when the effect is bypassed. I also added a DPDT switch to select between buffered bypass with tails and true
bypass. I took the idea from Merlin's Small Time Delay.
These are the changes to the board
This is the daughter board layout and offboard wiring
My DBD looks like this
I mounted the daughter board on the side of the enclosure, next to the output jack.