More complicated to make than the bottom bracket version. Once again, I've custom made this one for a specific frame/crank combo, although this one will work for 28-36t chainrings.
It's made up from 6 separate pieces of 2.5mm carbon fibre sheet and an aluminium clamp which I had (I think these are used to add bottle cage mounts) and held together with super glue (Loctite 404 rubber reinforced type).
![Carbon fibre chain guide seat post mount - components](/gfx/pubs/1396247658_r1.jpg)
Total weight is 45g, so not super light like the BB version. Due to the chainline on this bicycle, the guide sits a fair way out from the seat tube, so I had to overbuild it a little to make sure it was strong enough. Even so, 45g for this type of guide is still as respectable weight.
Here's a few other views
On the bike:
![Carbon fibre chain guide seat post mount - components](/gfx/pubs/1396247950_r1.jpg)
Another angle:
![Carbon fibre chain guide seat post mount](/gfx/pubs/11859447_r1.jpg)