Go with the insulated male and female connectors, just try to find them smaller than 1/4". 1/4" will fit but I mean just barely. I would cut the wires about 1" from the opto, I cut them shorter and the wires wouldn't make the bend so I had to trim the top of connectors with angled wire cutters. Also identify each connector with a marker and you will need a pair of needle nose pliers to hold the one connector in the bookcase (the connectors fit together snugly, it'll just push down the bookcase without a good connection if you don't). Give me a shout if you have any problems, I could disassemble mine and give you a step by step with pics if you need it.