Technically you are in range.
OK, that is much better. Technically, since 435F is the lycoming limit for continuous cruise, and around 500F for short term (climb) you do not need to do anything as an emergency. However, the system is not performing with the average of the field. Roughly if OAT was 100F then it could be ~420F for the CHT.
If you took a poll of regular RV operators, you would probably get the recommendation to do some "tuning" to the cooling system. That would mean sealing the baffle-to-cowl areas and aluminum baffle-to-case leakages. A guess, is that much of this could be done without any hardware changes and could reduce CHT 20-40F.
These leaks may not be obvious and some downright subtle, but they all add up. One area of concern could be geometry around your inlets, and how the air might flow there.
The next time you have your cowl off, if you could take pictures of the all the sealing areas around the cowl, and then around the engine, they can be easily posted here and you can get some expert comments.
Meanwhile
click this and you can read a good bit about the various questions and answers. It's a forum, so add salt.
Last item, if your fuel system is carbureted, then it could be a mixture issue and ignition timing is a big factor so if you have mags, it is an easy check. Overall, being a James cowl, I would certainly start with the sealing path before anything else.