I use ultra cam and 450+ strings on Wings from the 60s....also Bears, Black Widows, Drakes, Howatts, and others. Having shot at least 10,000 shots with such strings and old bows and never having an incident, I am convinced that the right string construction, the right bow tip construction, and a heavy enough arrow are all that is necessary. And, by the way, the draw weight of the bow has nothing to do with it. True, a 60# plus classic recurve bow may be more likely to blow up than a 40# version of the same, but I think that risk is due to other factors than string material.
Beginning back in the early 90s, I ask many bowyers what they did to "make a bow for FF"....that was the big phrase back then. I still ask that question regularly and it is amazing how often I get a totally different answer!! 20 years later, there are still more answers, but the only answer I agree with is that the tips need a strong material(glass,phenolic, or some micartas)and the tips and nocks should be shaped to spread the impact of string recovery.
I'm tired of the claim that where there's smoke there must be fire. Sometimes someone is just blowing it all around! I have seen only one bow that was damaged by low-stretch material: a guy put such a string on a Howatt Hi-Speed which didn't have any tip overlays on the back. The string loops were not padded, and-lo and behold!-the string darn well did crack the back limb lam. I pad my loops on every low-stretch string I make, regardless of what bow it is intended for.
As others have said in this thread and many others: it is your choice. Well, yes, but others are advising that it is not worth the risk! What risk, exactly? I've been "living on the edge" regarding this string material question for 5 or 6 years now with some of the most respected classic bows in recent history. Hey fellows, I've still got them all and still enjoy shooting them.
But, they'll claim the risk is not worth a few fps.....once again, not based on fact. Admittedly, the speed difference is negligible(but it IS there). But,so many bows are so much nicer to shoot. Sound, vibration, shock - when reduced- are all stealing less energy that should go to your arrow. Knowing what I know now, I'd use these strings if they didn't contribute ANY extra speed to the arrow.
Once again, this is just my opinion. You should form your own.
Regards,