Waveguides that are made of copper have a high deadweight. Specific gravity 8,9 g/dm . This might be to the detriment of some applications. I you want to reduce weight by creating thinner walls you will soon hit the brick wall because of subsiding stability.
You can, of course, apply a jacket afterwards but for that you also need a minimum of wall thickness. It’s more effective to strip the required copperlayer-thickness to the core and to apply an as light material as possible (e.g. with carbon fibre reinforced synthetic resin) on the coat afterwards and to seperate the waveguide from the core after its hardening.
The results for the experimental piece you can see on the picture are those:
The soldering version:
Meterweight: aprox. 16,6kg
The galvanic CFK sheated version: