About the logging, I suppose the next question is whether that degrades performance and what might be done about it.

I have learned that 3d party wx programs don't always play well with complex addons.  FSX does not do a horrible job, and the main advantage I am getting from REX is better textures.  I like the product and those guys, but they are still working out a lot of kinks.  If it lives up to its potential, it will be one of the greatest add-ons ever.  It is admittedly anecdotal evidence, but since the only problems I have had were when I used REX, I am satisfied it is to be avoided with this particular airplane.