I've been convinced that a port is essential to dry the boat out. Personal preference on where it goes. I've seen them near the mast, halfway between the mast and the centerboard on the deck, next to the centerboard on the slanted part, and on the aft deck either side of the traveller. I cut one in my boat this summer. My boat was dry, but damp with condensation. It was damp when I cut into it and dry as a bone in a few hours. I'm glad I did it.
Thanks for the picture. It is not like any inspection port I have ever seen. Perhaps someone else in TLF can identify it.
The most common around here are the Viking units available from Annapolis Performance Sailing. This port, combined with a "Fat Bag" gives you both access and storage.
If you want to get access to the interior at that particular point, you can put another port on the other side of the daggarboard trunk. The other option is to remove the current compartment and install a Viking unit in its place (this assumes that the two are the same diameter).
If you just want to be able to have a look inside and dry out the interior (always a good idea), simply put a Viking port on the foredeck near the mast step. This way, you can inspect it as well.
That's a big No! I had hoped that would be the case for mine. But sticking my pinky in the plug I could tell it was damp. My hull never leaked and when I cut the port hole, it was damp all over. It dried in hours with the hole there. The guy who gave me instructions, who is the local laser guru, said every boat he's cut open has had the same condensation moisture in them. He thinks if you want the hull to dry out inside, it needs a port. After my experience, I'd have to agree. Granted, this was the first boat I cut open.
Assuming you are referring to the drain plug on the transom, Hoffy's answer is correct. The 1979 I worked on this spring had been in a barn for years with the drain plug out and was still wet inside. As mentioned before, it is tough to cut a hole in something like a boat but If you want to keep this boat in good shape, an inspection port is a cheap inventment. Hell for the 1979 project, I had to install 3 ports!! See link below.
If you look at the thread regarding my hull separation repair, you will see a 3/4 hp drill and a 5½" diameter hole saw. I was lucky to be able to borrow the drill from a co-worker and the hole saw from my place of business. Getting a big drill is not a big deal - you can probably rent one at a big box home center. However, a 5½" hole saw is pretty rare. Most places only have 5" ones. The alternative is a jigsaw with a new, very sharp blade. In fact, this seems to be what most people use. If you don't have a good one (i.e. DeWalt or Bosch), I would borrow one. The cheap saws don't have a roller guide in back of the blade and this is key.
BTW how is the weather in Kansas? Ever been to Coffeyville?