I've not come across anyone, including NP, who is fusing the F5 PSU. When I built my F3 (stereo version), the PSU board was made for use only with Jensen 4 pole electrolytics and pads for fuses in each channel were placed on the pcb after rectification/filtering just before the DC connections to the rails. The board was designed by a friend who considered theses fuses an added safety measure. In addition there was the usual fuse for AC at the IEC. I have cviller's PSU boards for the F5 build. It's been suggested to me that rail fuses are more relevant on class AB amps than A, but I have found no definitive answer concerning whether they are necessary and, if so, why. Will appreciate some input on this topic.