Yeah, I used to squeeze my potatoes to guess at doneness, until I picked up the 210 trick. Now I just give them a poke with my probe thermometer and I know if they are done.
BTW, my favorite way to roast potatoes is to scrub them clean, then toss them in some olive oil and sea salt. The dry heat makes the skins all crispy and delicious, and you can dust off any excess salt when they are done. I usually tuck potatoes in next to whole chickens or roasts when I'm roasting them. A little something for nothing.
And another thing: you geniuses turned me on to 'cooking in the basement', aka putting potatoes and other foods on the *bottom rack* of the kettle to cook underneath other items. I haven't tried it yet, but I am fascinated, and can't wait!