Armatttan Mongoose RX Tray/SMA mount

thingiverse

Here's a small piece that fills the gap at the rear of the Armattan Mongoose. This lets you mount a small receiver like the FrSky R-XSR or XFire Nano. The top half has a mount for an SMA connector. You can also use this to attach a half-board VTX without screwing it into the top plate, which is my personal preference. As a bonus, there's enough space between the two halves to run your lipo lead through it. In my case, I routed mine on either side of the VTX antenna and it holds it in place nicely.