When splicing a hitch cord to the D, you have 2 options.
Easiest is go with a standard prusik knot. If you can't be happy with that, you will have to do some fussing with the ropes. You can't splice the thing on and then expect to be able to turn that into a VT or martín or something like that. You might have to form the hitch, keep it loosely tied, then splice it with the hitch tied.
Sounds crazy because it is. But when it works, it's pretty awesome.
love
nick