210 is normal for newer engines, 220 or even 230 isn't uncommon. I would try and see if it will climb much over the 210-220 degree range. It is entirely possible that it will stop rising. One thing to consider, though, is the condition of the rad. I know you flushed the coolant, but did you happen to look through the rad with a light? The fins could be partially blocks, and not allowing enogh heat transfer when stopped. Spray it down with degreaser (engine shampoo works) and wash it out with a pressure washer set up on medium pressure. You'll probably be suprised at the amount og crud that will wash out.