I have 8000 Lipos - my charger has the option for 1A up to 2A when using Storage Mode.
With my mah being so high - is it better for battery "health" to charge with 1A or 2A when set to "Storage"?
Both 1A and 2A are under 8A which is the 1C charge rating for your pack. Neither 1A or 2A will cause any harm they will just take forever to get it from LVD to storage voltage. Personally I'd charge at the standard balance charge as close to 8A (without going over) as possible and I would just keep an eye on it and switch it over to "Storage Mode" when you get close to 3.8v/c.
Anything less than 1C is not treating the battery any nicer.
On a side note... being able to storage charge at the full capability of the charger is another nice feature of higher end (yet not always extremely expensive) charger.
Whatever it is I just typed... could be wrong.