The PICO Drums seems like a poor choice to me, especially if you have drums on some of your other devices (like the Elektron gear). It would make a lot more sense to have gone with a PICO DSP so that you can have mono-to-stereo FX as part of the build. This would leave 1 hp (like it does now) which I'd suggest you fill with a Konstant Labs Power Checker...probably the smartest thing anyone can put in a 1 hp 'hole'.
The other thing I'm puzzling over is that if this is in a Happy Ending mounting and not something with a powered cab, where's your power supply?