This is such an interesting thread. I found myself nodding my head reading John Rinker's note. I bought my Hunq new in 2012, and I never thought about trail per se until 3 or 4 years ago when it seemed trail was in the air, everywhere I turned, and everyone was talking about it. Maybe it's something particular to the Hunqapillar compared with other frames, but I've never felt a need to ruminate over what I had on a front rack or rear rack, balancing loads, whatever. I just never had to think about it. It has always felt stable whether the front was loaded with nothing in the rear, or vice versa, or both front and rear were loaded, or without any load at all. That's not to say that hauling a good sized watermelon on the front rack — which is common for me during the season — doesn't change handling characteristics. It certainly does, but not anywhere close to a degree that I find uncomfortable or problematic at all. I carry what I need to carry, I do what I need to do, and my riding adjusts and compensates accordingly, with little thought about it. It's natural. Anyway, I think we are constantly adjusting how we ride due to varying surfaces, wind patterns, energy or fatigue level, tire pressure, how our muscles and brains feel, elevation, and so on. There are countless dynamic variables that affect handling, requiring us to adjust and readjust on the fly and then we get momentum. On the Hunq, for me at least, the net outcome is a sense of stability, comfort, and confidence regardless of how much I am hauling or where the haul is positioned on the bike.
Except when I experienced a puzzling shimmy. The handlebar would vibrate and swing wildly back and forth at speed if I removed one or both hands from the bar. The oscillation was palpable, annoying, and very much out of character for the bike. It was not related to any front or rear load dynamics, nor to any lights, bells, or mirror mounted to the handlebar. The shimmy would diminish a bit if I touched either leg to the top tub or diagonal tube, but not completely. I bought an IRD double roller bearing headset thinking it might solve the problem (Rivendell was out of stock of their Tange/IRD NeedL BlastR at the time). But before having the new one installed, I reached out to Rivendell to ask about shimmy. In typical transparent and helpful fashion, Grant and Mark both said (paraphrasing): sometimes shimmy happens for no apparent or solvable reason. Bike physics and dynamics are super complicated. Keep your hands on the bar, don't ride ride no-handedly! Try removing the racks (it didn't help).
Finally Grant said, no need to spend money on a new headset. It doesn't always solve the problem. Try heavier grease in your headset, and tighten it down more than you normally would. You're not after "buttery smooth" movement. You want some friction and resistance. It won't interfere with steering.
Sure enough, these simple steps completely eliminated the shimmy. Stability returned to the Hunq!
I wished I had contacted Riv before I bought the new headset. It's a nice piece of kit, now taking up space in the parts bin.