Hi George,
The point to the Q&A in my previous post is that we don’t even know if an SR Black 5 amp fuse should truly be considered to be a 5 amp fuse, as opposed to a 4 amp fuse or something even lower. And the reports we’ve seen from a number of people of blown SR fuses would seem to suggest that one of the latter possibilities could very well be the case, for many if not most or all ratings. Also, fuse derating (the margin between the current rating a designer has chosen for a fuse and the amount of current it conducts under normal conditions) is not a precise science, with designer preferences, the limited number of choices that are imposed by standard rating values, and turn-on inrush currents and other characteristics of the particular design all factoring into it.
So my basic intention is to provide food for thought, rather than advocacy. Although per my various posts on the subject I would not consider it to be an unreasonable course of action for someone who wants to try SR fuses to choose values that are one or even two increments higher than stock, and in the end perhaps avoid wasting several hundred dollars as a result. I respect the fact that your opinion differs, and as I said earlier, given the lack of meaningful technical data on the SR fuses I don’t think anyone can provide an answer to this question with certainty.
Regards,
-- Al