perhaps I don't understand the way the player internals work, but why not just have hijack have the option of capping the boot volume in the config.ini with something like

[hijack]
max_boot_volume=-20

and then hijack would just update the stored player volume if it exceeded this. the setting could then default to +10 (no limiting). would such a solution work better than using flash bits?

Edit: aarg, my idea's been suggested.

just though to have it work the way this thread suggested it'd need to be:

[hijack]
boot_volume=-16

and have no effect if not present.