Chances are, if any RC looks "lengthy and picky" it will be declined more often than accepted. That's been my experience.  The best thing to do would be to find a way to be as brief as possible and post both conditions at the same time.

It is possible to turn your RC on and off, and I suppose you could tailor the conditions for each request, but I think you would want to wait until each transaction had been accepted before you request another with different RC.

you could put all of the RC's in one but separate them out for certain types of books.  it may or may not work but that is the only way to have varied RC's.  of course if people read them they may not understand so if you do put varied on there make sure you are very clear what the RC's are for