i'm pretty sure if the power wire from the back of the futaba is in tact, it's gonna draw on all of em the same time and make a weird voltage problem, no? 3s and 2s parallel? if that's the case, be careful. That plug comes apart at the radio side that you can snip or remove the wire. i had to make mine before it was snapped so i removed the + just using normal guy thinking, didn't read the manual about it. my futaba 8j is 4.8 volt
sails, have you ever tried using rates, expo or subtrims? i know not so important from mr's, but mine didn't, only worked in trainer mode and then it just sent out raw unmixed ppm. That was the whole reason i swapped over to futaba
regarding dji's ppm, there gonna have to stop being so closed source and at least make a ppm setup screen that you can assign channels to. otherwise the whole futaba/jr,spektrum thing is gonna get even more screwed up. I've used Eagle Tree osd pro that uses the ppm signal for flight control and it has a screen you can go into and make the different ppm signals to different channels