I'm in the process of assembling a touring bike. I need to better understand the risks of using ~5cm worth of headset spacers in-between the stem and headset.

Facts:

Frame (head tube) = Gunnar Grand Tour
headset = 1 – 1/8" King NoThreadSet
stem = Ritchey Pro road 110mm/17 degrees, recommended by the fitter
handlebars = Nitto Noodle
spacers = King
fork = Gunnar Grand Tour

I weigh 205 lbs, I am 6'4"

Bottom line, these parts are nice and exhibit tight tolerances. I understand the higher the position of the stem on a steerer tube, the more leverage a rider would have to put force/stress on the headset, steerer tube, and headtube. I believe this is why Waterford recommends:

"Threadless headsets: Gunnar recommends against installing more
than 40mm of headset spacers on its steel forks. Review with the manufacturer
for limits on separately purchased forks."

But, they don't state that a rider can't do it, or shouldn't do it. I've had 7cm worth of spacer's on my street single speed for almost a year. I treat it with respect but I ride it pretty hard. I haven't noticed any deformation of the headtube, steerer tube, or headset... yet.

I need the ~5cm worth of spacers in order to achieve a 2cm handlebar over seat position; a nearly ideal position according to a fitting process I went thorough. I'm planning on riding this bike aggressively and hard at times. What does it take to deform a headtube, steerer tube, and ruin a headset? Any other tall, big, and heavy riders who use a lot of headset spacers on their bikes?