I can definitely see where 20 pounds can fill up quickly. There is another rack to consider, the Thule Tour Rack, which works with a full suspension bike. However, similarly to the Topeak one I mentioned, the weight rating is not very high. If you use two panniers and put items on top of the rack it can hold 25 pounds. It can only carry 15 pounds in the panniers.

Are you using any other bags on your bike? As it is a full suspension bike I'm guessing there isn't much room for a frame bag. You could think about a handlebar bag or a down tube bag. You could also consider one of those Thule racks for the front of your bike as well. Every little bit helps when you're trying to keep your weight down!

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