I couldnt open your schematic. But anyways, let me see if I have this straight? On the first scenario are you saying you want to run a window switch or two window switches? like have the first 75 kick in at 3000 and then the second 75 kick in at 4900 and then both shut off a hundred or so rpm before shift point?
To do that I believe you will need two window switches or a device capable of switching two seperate items. And as far as spraying both stages after the shifts..thats ok..youll be in the rpm range, after launching, that you will want to keep both stages activated. At that point traction will not be an issue and your rpm will be high enough that large tq spikes will not be a concern.
For the second scenario...its about the same as the first...except you will spray a 75 shot through the shifts. But again...after launch and the second stage kicks in....it will likely never drop out again except during the shift.
I think this is what your where asking? And also I dont own an auto and have never raced an auto with nitrous so I may be talking out my ***. Just wanted to get the conversation started for you