Does extensions matters?

Well, at least quality does. What absolutely is crucial is that the extension does not brake. A racesail require about 500 kg of downhaul, a different ballpark compared to a wavesail. As you can see, my extension bag is filled with extensions from various makes. I have tested a few. And I must say that the price has correlation with the quality. All of them works from the beginning but after 20-30 days the cheapest are worn out. Plastic parts cracks, the pins in the collar breaks etc. In general the RDM with often more simple collar construction are holding together better than the SDM´s. But RDM is also often more used to smaller sails with not so much load.

Not the best angle, the rope gets worn.

Much better angle, with the Nylon part.

Alu or Carbon? Well a more a matter of feeling than performance. Carbon does not corrodes though… 

Which one is the best? Well I have been quite happy with Chinook for some years, but right now I test Neil Pryde MXT Carbon. All good? Well there are problems with them too. This year NP have change the angle in the cleat. So when I used a standard rig-winch the rope got worn off immediately. I had to build a new winch with a different angle. Maybe not a problem for NP-riders, but for Naish and Loft Sails, that have the downhaul block in another angle it did not work. But my tips is, go for quality. A good extension last for many years, a cheap one a few months.