Default [Q] Ramos i8 as USB mass storage

As there is no "Ramos" at the device-specific section, Iīll put my question in here. Hope, thatīs o.k.

I have successfully rooted the Ramos i8 (Android 4.2.2), but I canīt get the usb mass storage mode working. It only works as MTP-device, which sucks. When I enter

setprop persist.sys.usb.config mass_storage
in a rooted shell or via adb (also as root), the MTP mode stops and the device disappears as a MTP in Windows (when connected via USB). But the device does not come up as a mass storage device, even not after dis- and reconnecting the USB-cable or after a reboot. Vice versa, it works:

setprop persist.sys.usb.config mtp
Any ideas how to get the USB mass storage mode working?