Today (Sept 10, ’16) I drilled the holes and added the new rails. A couple of the holes were slightly out of alignment but the rails now fit and look good. I have to countersink the coachbolts, and one hole in the coachroof has lost is thread. i will fill the hole with resin and cut a new thread. Then I can cut the rails to length, round off the ends (is that “chamfer?” I shall check!) and perhaps round off the edges as well.
I do not think there is enough depth to the rail for me to make and put caps over the bolt heads, but if there is, I will use the spare 12″ of teak to make them. Small circles of teak to sit over the bolt heads and hide them.
The next decision is – oil or varnish? Dunno. Oil is more practical, varnish more beautiful.
frankjustfrank 
You can’t varnish teak, it’s too lovely and has its own oil in the wood to protect it. Teak oil applied occasionally is so easy, but re varnishing is tedious!
Thanks Sue!
The previous layers are just about worn off the old rails, as well as the toe rails. The cockpit teak looks shabby but will soon be back to bare, with a little help from me.
I was advised to use Cetol, and Vyv had commented on the sun of the Med causing his coachroof rails to disappear under the sun, when left bare.
The upside of just using oil is that I don’t have a shabby boat every 12-18 months – will oil protect the teak from the sun?
Are you still in the Med?