the firmware is confusing!!
i have a ds-7204huh which is on firmware v3.5.50
but looks like i can install v4.1.00
but does say this
For DS-7204HUHI-K1/P & DS-7208/16HUHI-K2/P, please don’t upgrade the firmware from V3.5.50 directly to the released version, otherwise they will be defaulted
so...