I don't think 210 is unreasonable or anything to worry about in those conditions as long as it stablizes. if it keeps climbing and/or stays above 230, then I'd be concerned. Heck there's plenty of engines that came with 195 deg thermostats.
I think its totally doable. It may be take some testing (trial and error). It also may need a hair less timing. That would probably be just a an adjustment on the vacuum advance. On the road race engines, the guys are running less timing than the drag race guys.* Big difference in engine temps between running an engine for a short burst versus one thats running for hours and hours. Its one reason the factory timing was on the slightly conservative side. They wanted to cover the worst case conditions while still providing good power and milage.
*These guys all use the same tuner. Tim Herron (All time racing), Ott (RiP) and Hagstrom, Mike Ritz (Team Starfish racing tribute) are three I know of.
