Got the holes drilled through the floor in all the rooms where they need to be, fed the cable pairs through, and cleaned out the closet that has the hatch so I could take a look down there.
As you can tell, I'm apprehensive about diving under the house, but after I pulled the hatch and stuck a drop light down there, it doesn't look *too* bad. The dirt is dry, and looks pretty well compacted, and best of all, I measured 27" from the "floor" to the bottom edge of the joists.
YAY! I won't have to worry about getting stuck while I'm crawling around down there!
There was a nice breeze coming up through the hatch, and *NO* foul odors of any sort, so I'm guessing we don't have any plumbing leaks. I even took one of my small low-light video cameras, connected it to a old monitor I have, and "probed" around under the house as far as I could reach with the pole I had the camera mounted to. No beady eyes stared back at me, and it looked remarkably free of cobwebs and other junk.
If all goes as planned, all I should have to do is crawl about 15' to each cable pair, and bring them back to the hatch area. I've drilled holes through the floor in the closet by one of the side walls, and that's where I'll bring the cables back up through the floor to connect to the splitters and 8-port Ethernet switch that I mounted on the plastic plate today.
I was going to use a piece of plywood, and then I remembered I had several plastic cutting boards left over from a project, so I grabbed one of those and used it. It's easy to drill, doesn't splinter, and doesn't need to be painted to look nice. I've used various sizes of plastic cutting boards to mount radio stuff on over the years, and a bonus is that they even have a handle built-in!