I want to buy a LC18 frameset and add an aero bar for long distance rides. Is the SPCycle bar the only option or are there any new options?

So for mixed use steel spokes are the way to go right?
@Serge_K: I think you are pretty spot on. So for the 32mm tires do you think the 26 iw rims create a good transition between rim and tire?
For the 30int/36ext it would be nice if Peter could test the real world measurements of a 35mm tires. I think there will be more demand for 35 and 40mm road tires in the future, like the new GP 5000.

What does SD01 and SD02 mean?

The Lightcarbon seatposts

I am in 

I already follow this thread for a long time and I am aware of the issues in the past. However it seems to be hard to find another frame which is light and still is quite aero like this one.

Will the XM Carbon Speed wheels with 26mm internal 34 external paired with a GP5000 32mm fit in this frame?
Did anyone ride light gravel with this frame?

45mm is gravel territory, so i wouldn't want to ride that as a road bike (i tried, didn't work for me). Afaik, a "do it all" bike a la Vitus (recently featured on GCN) has clearance for up to 38C, not 45C.
In my experience, it's also annoying to change wheelsets, because rotors tend to rub, and it's just irritating to swap wheels.
My conclusion, having tried the one bike to rule them all, is that it doesn't work, and you end up with a shitty road bike and a shitty gravel bike. For most friends my size, i'd put them on something that clears 35 or 38C with slick tyres, aero, that being some really versatile, really fast road bike. Peter from Xiamen carbon speed is about to release such frame (you may be too tall).

How about the CS-GR01?