I think probably -- ask your sailmaker! -- a tri-radial main for a cat is more demanding on the sailcloth because there's little heel to absorb gusts. So normal Dacron can certainly be used, but will likely bag out fairly quickly.
I'm just in the process of having a tri-radial main made for my large mono. Here again, because of the size of the sail, Dacron is possible (the old one was) but is not really recommended. Hydranet is as expensive as laminate and gets mixed reviews
(many loves, but many others who say that it behaves just like Dacron).
Laminates have gotten much better in recent years -- why not go with that? I'm using a carbon-fiber and Vectran reinforced laminate. The cloth is autoclaved, not just glued, and apparently impervious to delamination
. It is made in the US and not the Far East, but it is no more expensive than Hydranet and is only about double the cost of really good Dacron.
If you do go with Dacron, keep in mind that it comes in very, very different quality grades. The good stuff is not cheap
. The cheap
stuff will not hold its shape like the good stuff. And beyond a certain size sail, even good Dacron is not really going to hold its shape.