Backpacks should be placed straps up to avoid tangling in the spokes. They need at least 2 bungies. In wet conditions, a rear fender wil keep the bag clean.

I have toured for a week with a small loaded backpack bungied to the rack.

I attatch bungies to the lower part of the leg or wrap them around the top platform, whatever works.

For larger and heavier loads such as bags of cement or plaster, I have made a platform extender , just a bit of plywood with some holes, that I wire to the platform.