external payload

Greetings all, I am working on a project where I must simultaneously capture video in two directions. Can anyone recommend a decent (and lightweight <100g) true 4k video camera? Additionally, where is the best place to mount the camera without obstructing its downward vision, significantly...

I have been working on an external GPS location tracker based on the particle photon and electron. I am prepared to use a single cell lipo but would like to see if there is an elegant way to tap into the flight battery. I don't think I can use that micro usb port on the side while in flight...