Brian, I've read those articles before...I'm not using much down pressure so as to push down on the panel. These are narrow low spots anyways, ones that couldn't be created from pushing down on the panel.
I'm using new sandpaper, but of course as you can see it's not a very course grit for blocking. What grit are you using to cut it down?
I've read Henry's thread before too. The hood is actually laying flat on a large rolling table that's actually the same size as the hood so I don't have any parts of the saw horse stand pushing up on the skin anywhere.