The piece I would add for peace of mind is a strut between the handlebars at the stem and the SwingGrip at the cross tube. I would feel far more comfortable hitting a bump or heave at speed. Even just a strap between the two would help but that would tend to want to pull the cross tube back and add some compression and upward bending to the SwingGrip.

I have bike that tends to speed wobbles; getting worse as I age and become more timid. I just purchased an Arundel HB bag; now strapped to the bars, to see if that will help. If so, I am looking a good decaleur. Bike's got a 1" threadless and minimum spacers, 120mm -17 stem. (I've never been fan of HB bags but if this works, I'm willing to change. I love this bike but I want the grin of the descent back!) I'm open to ideas.