Iroko has a very uneven grain, charactarised by being virtually impossible to plane and also blunts tools very quickly. So, although Paul was told it was iroko, I think it was nonetheless still teak and he was mis-informed. Paul and I did debate this when he submitted the article for publication. On my 35 Classic, I have replaced some of the teak, with teak slavaged from a settee runner, and it looks the same. I would advocate assuming it is really teak, even if the grain is slight wavy and uneven.
Teak is now virtually impossible to source as new stock, so you are into salvage territory, looking on ebay etc. The important think is to make sure that the teak plank is cut along the grain, as some stock is cut slightly across the grain. This makes it weaker and expose the end grain, which will both affect the aesthetic look and its durability.
normally the teak is just bedded down straight onto the fibreglass moulding with the caulking mastic.
Be sure to check-out my article on recalking teak in the 116 edition (Spring 2020, page 13) of the Dufour News, available in the Dufour News Archive section of this site.
Depending on the size /quantity of teak you need, I 'might' be able to supply you some from the remains of my settee runners.