ok i would like to run a full stack using 2 marshall 4x12 cabinets with speaker configuration that is not original ,but both cabs are wired correctly and both cabs have 4 8 ohm speakers in them so a total of 4 ohms load ,but my jcm 900 only has 8 and 16 ohm options . what to do ? i am aware of cab lynk ,but i don't know what config my cabs are? series? parallell? series-parallell? they have the same wiring as marshall 4x12's that use that 4,8,16 ,mono ,stereo switch . also i can run like that easy with my marshall jcm 800 2 cabs 8 ohms each for a 4 ohm load and the amp has that covered ,but ,imagine if i pull 2 tubes for a 50 watt amp the impedence gets cut in half? so how?