Middle Cleat on 312?

There is an area foreseen to mount the cleats on. On mine there's a piece of aluminium moulded in to the deck.

I bought the cleats from SVB: https://www.svb24.com/en/pfeiffer-cleat-with-base.html on mine the toe rail is of Pfeiffer-system.

I have not done it yet, I bought all the parts, and I think it's going to be pretty straight forward.

Drill 10.5 mm hole in deck until aluminium plate. Drill tat with 8,5mm drill, and cut a 10mm thread in the aluplate. 

Apply Sikaflex and tighten the 2 M10 stainless bolts. 

On mine there is a plate moulded in to the deck. 

No. 

The aluminium plate is inside the glassfibre. So I would drill 10.5mm in the glassfibre until the aluplate, and then 8.5mm in the aluplate and the glassfibre on the underside of the aluplate.

And then I would use one of these to make a M10 thread.

If you need it, I will try and find the details.

Kox

I think the one I use is this larger one, with the end caps, so that I can switch it from one side to the other

(also available from svb?)

You may be right about its strength, (though I am not certain) but I use it when I am "parking" the boat.  I either use it just as a mid-line when we first come alongside a pontoon, or as a part of my "parking line" system when I am coming onto a finger pontoon.  See here

As seen in the photo, once alongside, I run bow and stern springs from the ends of the boat onto a mid cleat on the pontoon, and this makes it easy to adjust the boat's position.