No, never considered it, but my old West Marine hard rowing dinghy had a little pocket under a similar central port to hold things. I found out the hard way that the cover was not completely waterproof so I started using a dry bag instead.
I find the inspection ports on my Legacy to be really difficult to get off due to the rubber gasket and I kinda like it that way for safety. Being in the relatively wet, wide open cockpit of a fairly active, low freeboard boat, I would try to keep those ports closed all the time while sailing. If you suffer a knockdown for any reason, it could sink the boat very quickly were it on the leeward side. And if the cover is removed, it could be very easy to lose it off the back as the transom there is only about an inch high over the slippery fiberglass cockpit seat.
I find that the main cabin is close enough to stow things just inside the hatch, and if the weather gets nasty, it's easy enough to close the hatch boards for dryness and for safety. And it's a lot harder to lose phones/keys overboard being stored there rather than the slippery seats with such a low transom edge.
In addition, I find my Legacy to be a really dry boat inside. Meaning I never find any water in the bilges since there are no through-hulls. If you were to open those inspection ports a lot, you could be introducing incidental dirt/water into the bilges, which could then cause odor and mold/mildew if you didn't keep it very clean. So, sorry to sound so negative, but I would not recommend it.