The ARRI/501 Side Loading Baseplate (LWS 15 mm) from Kondor Blue is designed for BMPCC 4K/6K camera cages and features an ARRI-standard dovetail to support 15 mm LWS rods.
You can create a setup with a big lens and a large matte box, which enables easy camera mounting.
It is rubber padded to minimise any twisting and prevent the camera from scratches.