Will the VARIA's mount fit Argon E117 seatpost? (which is flat, long and rectangle)

The aero seatpost adapter fits nicely on my Specialized Shiv which appears to have a similar seatpost. You get two rubber washers that cover a suitable range of aero seatposts so my guess would be that you are fine. Might want to check out a local bike shop (and buy it from them) to be totally sure.

definitely not without some DIY and taping on top. the mount angle is too steep rendering the mount unstable. i have added some tape on top of the doubled whashers to cover the seatpost, but still the mount will unavoidably not stay perfectly centered. trying to find a 3d printing company but no luck so far. thought i had found the solution with Shapeways but the reviews are not really confidence inspiring...