Unless it's changed in the last year or two, BCY makes a material exclusively for Martin Archery called "Helix" or "Double Helix" (I forget), which is a FF type material.
Don't just take the properties of non stretch strings as value though.
That depends on what "properties" you are talking about. If someone says "I picked up 38 fps and had to go 3 arrow spines heavier just by switching strings!", then I agree with you--you can't take such claims seriously--it's just not going to happen.
However, the facts are the FF type materials are much more durable and have much less stretch/creep than any dacron string material (B-50, B-500, or B-55). Since they have much less stretch, the bow can be braced lower than it normally can with dacron.
Preferances still vary though--shoot what you like. I prefer Dynaflight '97 and Formula 8125.
Chad