FPV Frame Super RC Range 3 Inch

Specifications
Flight Controller Mount: 16x16mm
VTX Mount (Rear): 20x20mm
Arms: 3mm
Other Plates: 1.5mm

This is still my go-to frame for a true lightweight 3 inch. Note that you will however need a flight controller with a  16 x 16 Mounting pattern.  I have used this in both analog and digital builds with a  naked vista mounted in the rear.