Led lights help

Hello, I have these led lights i want to install in my sofit. The power supply is DC 12v PRI is AC 90-264v 50-60 Hz 5-15w max. The lights are 0.6 watts and i have 16 of them. I want to run about 150ft my concern is the voltage drop. So far I hooked I did an experiment and hooked about 100 ft of 24 awg solid copper wire to the 22awg braded copper wire of the lights and transformer. At the start (after transformer)im reading with my meter 12.29. At the end of the 100ft (before the lights) im reading 11.90. At the (end of my 16 lights) all ran in a series im getting 11.33. I have to add more wire about 50. Once i do this can I take a reading to tell if its going to work or not? What numer is to little?
Thank you guys.