Somebody asked about sitpost insertion length: my "S" frame only had about 13.5cm, measured from the edge of the sitpost's tube, not from the actuator.
Looking down the sit tube, it appeared as if the insertion should have been much longer: the tube was open all the way down to the shock mount.
Upon further inspection, I noticed what was stopping the sitpost: the top part of the sit tube has an inner carbon tube, which is the one where the sitpost slides, the same that is squeezed by the clamp.
This inner tube is somehow epoxied to the outer tube, which is part of the frame. The epoxy a the bottom of the inner tube bulged out in a few spots, reducing the diameter.
I decided that this was an unintended side effect of the assembly process and that it was not structural, hence I proceeded to painstakingly file down the bulging epoxy. This resulted into close-to-infinite insertion length
You should probably not try to do the same, unless you are sure that my "it is non structural" assumption is correct..
..but if you do, the best way I found to get it done is to tape some sandpaper to the bottom of a tube with a smaller outer diameter than the sitpost, say 25mm.
It is also useful to mark the "sanding tube" at the proper insertion length, to prevent sanding away anything else by the protruding epoxy: enlarging the sit tube diameter would probably be quite bad.
