I've a 2012 F650. Rode it cross-country (6,000 miles) fully loaded with Jesse bags, top case, passenger, etc. I've had NO shaking problems at 70mph+, on gravel, dirt, in rain, etc.
Suggest you look at the head bearings and tire pressure. Also, my preload is somewhere between 1/4 and 1/2. Perhaps yours being at full preload is adding to the problem.