Nice, thank you very much!I'm using the niterider Sabre 80.
I am not listening unless you give me links.Most run of the mill stuff like Cateye etc can be angled appropriately.
They also make these for seat stays that can be angled easily. be careful which one you pick as they do both battery and dynamo versions.B+M Secula
https://www.sjscycles.co.uk/lighting/busch-muller-secula-rear-light-seat-post-fitting/
You can fit most Cateye lights to a seatstay, and they even usually provide the correct size of clamp band, but that doesn't mean that the light can be aimed correctly. The LD610 in particular is impossible.
But not aimed horizontally at the same time.The Aldi F/R USB rechargeable light set can be mounted on the seat stay.
The mount seems to be rotatable to adjust angle.But not aimed horizontally at the same time.
The individual rear light can, just about, but you need an old-style frame, horizontal top tube and size 58 cm or larger, so the stays don't slope too much.
The point is that when you look at how far away the centre of the rearside of the light is from the mounting band, the length of the light, and the angle of the seatstays, you'll see that it won't tilt downwards enough to reach a horizontal aim before the bottom end of the light hits the seatstay.The mount seems to be rotatable to adjust angle.