/usr/local/etc/rc.loader.d/20-misc
autoboot_delay="400"
autoboot_delay="300"
Isn't it like most .d folders, that an additional file like 70-custom-delay with the same content would overwrite 20-misc? Like most of those files work in the Linux world? That way, the 20-misc can be overwritten from any update, but your setting would remain. I don't think, that the whole folder is overwritten/deleted at an update?Edit: first found value prevails. You need your custom file to be lower than 20.