I am sorry to hear about your issue with the Fargo, and I apologize for the inconvenience it caused you. However, I am curious as to whom you spoke with at Salsa about this issue. This is the first that we have heard of this particular issue. Again, I apologize if you made contact and were not responded to.
We have had a small amount of people report a shimmy with a heavier front load on the Fargo, and it typically lies with load placement. Due to the slacker head angle of the Fargo and the more "mountain" geometry, if the load is high, this is possible, but not common, as it also has to do with rider placement on the bike.
I will contact Topanga Creek today to thank them for helping you with this issue and to make sure their needs are met. If you have any additional needs, please feel free to contact me direct at tkrueger at salsacycles.com.
We stand behind our products 100%, and I feel this was just an issue of miscommunication, as we typically respond to emails or phone calls within 24 hours. Again, I am really sorry for your experience, and if there is anything I can do for you, please let me know.
Ride and Smile,
Tim, Salsa Cycles