Mmm couldn't say, the times I tried it was 60-70% filled. Contents were overshoes hydration tabs thin wool (suit) trousers a couple tshirts toothbrush soap etc, so mostly not heavy things. The top was folded over a few rolls and I have had extra straps on it to hold it tight against the seatpost and the frame. So your mileage may vary, but the load was not all on the saddle rails whenever I tried it.
In the end I was riding an ISM Adamo for greater comfort, so metal rails when loaded up heavier.
Mmm couldn't say, the times I tried it was 60-70% filled. Contents were overshoes hydration tabs thin wool (suit) trousers a couple tshirts toothbrush soap etc, so mostly not heavy things. The top was folded over a few rolls and I have had extra straps on it to hold it tight against the seatpost and the frame. So your mileage may vary, but the load was not all on the saddle rails whenever I tried it.
In the end I was riding an ISM Adamo for greater comfort, so metal rails when loaded up heavier.