Modified IDC connector (Floppy drive) cut in half and about half the connectors removed (every other socket) spacing is about perfect for LEDs if you file the base a little on each one.
Groups of four proved to be the best with the power configuration I'm using. Groups of four wired in series with each group wired in parallel with a rechargeable 9v battery. No limiting resistor is used since current is self limiting with 4 in series. 9v battery runs for at least a half hour with 16 LEDs. LEDs are overpowered for maximum brightness but I've only had one burn out so far. (socketing is essential) 8000mcd white LEDs., probably putting out 10,000.