Hey Phil, You could also mention to "your friend" that you could start with a higher output transformer kicking out 22 volts down that line. That would also help. A word of caution if doing this though, just make sure you know what the top end, input voltage range is on the LEDs your using so you don't exceed it. (It varies slightly from manufacturer to manufacturer) As long as you are not over the top end of the input voltage load of your LEDs, your good to go. You'll have to test the first light on the run with all the LEDs on the run wired up to know, (under full load) to make sure you are in the window. You can also "roughly"calculate it via traditional voltage drop calculations. Tip: When using high output transformers that exceed 15 volts, start testing with lower taps first, (ie. 14v and 15v) and work your way higher as you need to: starting too high and testing could have an adverse effect on your LED if it spikes way over recommended top end input. Better safe than sorry.
Have a great day- Tell "your friend" hello.