Let's talk about older bows. I'm shooting fastflight material on three old ones now. A D97 on a 1972 Bear Takedown, a 450+ on a 67 Shakespeare Necedah, and a TS-1 on a 1961 Bear Polar. I've not found the "too harsh" factor to be true....and if you remember correctly, I've been a B-50 friend for decades.
As a matter of fact, I find the newer strings to be less harsh, as far as vibration goes, than the B-50 dacron. The 1972 Bear Takedown is quieter and has much less vibration with the D-97 than a comparable B-50. The Shakespeare now has over 2000 arrows through it with 450+ and shoots quietly and like a bow five pounds heavier.
Nobody has done a study using new strings on old bows, so everything you hear is rumor, or based on one or two breakages that may have been a bow problem more than a string problem. That's why I have decided to give it a fair chance.
My bows show no ill-effect, or even moderate wear on the limb ends. I make sure they are rounded well, where the string loops over the limb, with no sharp edges. The up side is the extra overall performance, including a bow that is much more dead in the hand with very little vibration, as well as extra oomph.
By the way....the 450+ I'm using on the Shakespeare is a 6 strand with 12 strands in the loops.