 I just would do this. Go half of what they tell you you can go without a beam between them. Yikes, that's a David Doval answer. You'll never have a problem with them other than termites. If you've sprayed the bottom of the house, you won't have that problem. Wait, I got an idea. Fill your crawl space with concrete. There you go. I probably should have built a slab. No, I'm on a slab now.