Yes, broad opinions ...
I have an O' Day 25 that I replaced the bulkheads on. The chain plates are as Jackdaw said, about 18" long and 2 or so inches wide. They are thru bolted, not wood screws. You seem to be forming a broad opinion on something with only a small photo as your basis. True, the O'Day is not a "blue water" boat made for crossing oceans. That is not what it was designed for. It was designed as a coastal cruiser/lake sailor.
There is no need to take offense, CB ... I think we all form broad opinions with the information at hand. That's why I question what is shown in the photo. When you say thru-bolted, that means thru-bolted to what? What's on the other side.
Actually, this topic is near and dear to my heart. The attached photo shows my shroud fitting just in front of the areas underneath my windows that have soft decks. It's been a concern since I've had the boat, but the condition hasn't changed in all the years, other than I hope to have eliminated any further leaking.
The windows have a very cheap plastic frame and I anticipate replacing them with an aluminum-framed custom made product.
The photo of the interior shows the port side bulkhead which has been damaged by water intrusion through the shroud fitting. The dark staining shows the extent where water was in the wood. The interior hadn't been varnished before I varnished several years ago, and I was astonished that the moisture apparently was still in the wood. It never showed until after I varnished. Anyway, the bulkhead was damaged along the bottom where fasteners of wood to fiberglass where pretty meager looking to me. The bulkhead on the port side, 3/4" ply, had been flexing some and it was disturbing to me. So you can see that I reinforced the attachments with 3/4" strips of solid Ash, intended to look like trim, bolted thru the fiberglass to create a vice along the entire bottom of the bulkhead which has made it rock-solid, even though it looks like hell.
The chainplate is more than just a strap. It's at least 1/4" SS reinforced-webbed angle with the upper flange bolted thru to the part above deck, which is also a substantial hunk of metal. Then there are 12 bolts (3/8", I believe) thru the 3/4" ply to a another 1/4" thick plate on the other side.
The deck is sound around the shroud fitting and along the rail, so the springy decks don't really concern me. I re-bedded the shroud fitting which assures me that I'm no longer seeing water come thru to the inside. The bulkhead in between the speaker and the chainplate is weak though, so I am concerned about that. The next time I take the mast down to move the boat, I will replace the entire bulkhead with new wood.
I've put off the windows because of the expense ... and because of the windows, I've put off fixing the deck. At least I caulked them everywhere it looked like a source of water to keep it out temporarily until replacement. The new windows are going to be slightly larger than the old because the radius of aluminum can't be as tight as the plastic, so I look forward to repairing all of the core around the windows.
I put out a lot of money to re-power the boat last year, so the urgency to make her right everywhere else has really notched-up! How do you like my step-son's boat shoes!