I think i would have the defaults in a temporary hash and merge that with the users preferences:

my %default = ( foo => 1, bar => 2);
my %users = ( bar =>3 , baz => 2 );
my %CONFIG = ( %default, %users ); # user overrides default
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This way you shouldn't have to reset them, they get applied "on the fly."

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)