I keep seeing people talking about the gap size as a solution to the burning under the ring, but I don't know the thought behind it in terms of a larger or smaller gap. I have never had a custom device and am thinking about getting one, but I always have issues with burning under the scrotum and some on the upper right side of the ring. Does this indicate the need for a bigger or smaller gap?
generally a bigger gap will help with burning and a smaller gap will contribute to burning. I got one of those digital calipers on Amazon (relatively cheap) and took multiple measurements of my testicles and then took off a few mm to come up with my custom gap. It worked out really well and burning definitely was reduced. So make it as big as possible but smaller than your balls could possibly slip out of.