Come to think of it, the two 50' runs are on 12V now that I think about it, sorry for that.
I have plenty of other runs that combine a 10' 3-core extension cord from Ray and a 25' 3-core extension cord, so 35', using 18 AWG extension cords (again, I will stress that by no means am I guaranteeing that what is referred to from Ray as 18 AWG is actually 18 AWG, but it performs well). I just did the voltage drop calculator, and, assuming 35' feet distance, 5V DC, 18AWG wire, injecting power to 50 pixels, running pure white (which from my direct measurements equates to around 1.9A), voltage drop at 35 feet is only 0.89 V which is nothing to write home about. The reason I chose 50 pixels for my drop calculator is that, most of my display is setup as 100 pixels per output. I typically connect power and data to pixel #1 directly out of the controller and then I connect power only to pixel #100 (or pixel #50 depending on the particular element).