5mm is plenty could halve that and tie down to 1 1/4 yard.
Only ever come across two old BSA well over a decade ago where the gaps became larger, all others didn't work or reduced gap ranges and performed crap. Leave alone.
21 clicks at 1/8" is excessive looking half that, I would check if its holding zero having seen dozens that wont. Initial signs will seemingly be non progressive clicks ie big jumps in clicks for a couple of yards.