Anyone undersize their fuses?

Thinking about changing a couple fuse sizes in the fuse box, mainly looking at the radio/back up lights fuse. All that is on the circuit is going to be the back up lights and a volt gauge, so 20A fuse seems excessive. Anyone undersize this fuse to either a 15A or even 10A, or any other fuses for that matter? I have a fairly stripped down setup with no AC or extra electrical burdens so was thinking the stock fuse sizes could be overkill in a couple circumstances. It’s a 1972 Duster and I have all new harnesses due to previous owner had dash fire. Will be ammeter bypassing so looking for other opportunities to reduce risk lol.