Ron, There are 3 rooms on the first floor about 11x11'. They all tend to slope a bit towards the center of the house. I had considered putting in new flooring but I do like the personality of the old stuff.
I had just figured since I need to add more supports, a sub-floor and possibly jack the center support, having open access to the crawlspace would make all that much easier. I can be VERY careful removing the old planks.