Android/Nvidia Shield PPSSPP Control Mapping Issue

[FatFingerz]

Correct me if I'm wrong because I'm very inexperienced at this or I might interpret the problem incorrectly. You can't do that because the 2 analogs on Nvidia Shield share the same input for non-fully-optimized apps, such is the PPSSPP.
Might work if you use some kinda Bluez IME app on the market, like Gamepad Enabler for example (requires root) or some equivalence of Moga VK for Moga devices.
Hopefully you will be able to find a solution to your problem though.