I would have thought a ¼” screw is a bit on the small size, were the cleats fitted buy the builders? It’s now a bit difficult to do much with them as the threads are glassed in.
It would be difficult, not impossible to drill the threads out and fit bigger threads, possibly with bigger backing plates below, however a lot depends on the condition of what you are fixing through, the deck.
Also with ¼” screw, you don’t have a lot of room for corrosion (i.e. crevice) before the bolt is severely weakened, perhaps they should be pulled fairly regularly.
We have some very nice fabricated stainless steel mooring cleats and fairleads, the cleats are fixed through the deck with 8 No. 16mm countersunk machine screws through a 8” x ¼” steel flat running all the way around the hull.
The fairleads are fixed the same way but with 5 No. 16mm countersunk machine screws.
But then the boat was built in a yard where they build small tugs!!!!, 70 years ago.
When it is blowing hard and she is surging backwards and forwards the only thing that will give away will be the moorings on the quay or pontoon.
Over the years we have towed a few boats, a couple of them were in the 45ft size and again I don’t worry about our fixing point as our cleats are not going anywhere.
We are 48ft in length and around 22 tonnes.