Folding Bikes - Beam rack weight limits

I've been looking at a couple of beam racks for my folder, rated at 10kg. Is this limit to protect the rack itself, or to protect the seatpost to which it is attached? If the former, it seems to my eye that it would take a good deal more than 10kg to bend or damage this thing. If the latter, wouldn't it make a difference which part of the seatpost you attached it to, i.e. just beneath the saddle, or just above the wheel?

What are your thoughts?

When overloaded, the rack tends to pivot on the seatpost in turns at speed. Bad things happen when the pannier rails hit the rear tire. I've carried double the load rating, but used great care and slowed when turning (see Newton and inertia). Theoretically, if your lean angle is exactly right, the inertial moment of the load is aligned with the bike's path; if not, road rash or worse.

Thanks for that Maunakea. Does it make any difference where you place the rack on the seat post? Also, how would two racks, one above the other, neither overloaded, work out?

Lower is better, lower c/g is always more stable than higher c/g. I haven't tried two racks, but a beam rack itself is not light.... maybe a kg, and if you use a QR trunk, even more weight for the QR system. I would think about multiple bottle cages and putting heavy items in "bottle packs", and use the rack for bulky items, rather than try 2 beam racks. If you have more gear than that will accmmodate, I would think about changing to a different frame that accepts a strut-mounted rear rack. Strut-mounted racks are much lighter than beam racks.