I have a 50# Super Mag and it is a bit noisy too. I have tried B50, fast flight, DF97 and DF97 with B50 padded loops. Starting at 8" brace height and going up towards 9" a little at a time with the B50 helped. If I remember right, it was around 8 5/8" to 8 3/4" that was the quietest. It was a 14 strand string.
The fast flight was noisier, made a sharper sound. Raising the brace changed it some but was still noisier than I liked. A little bit faster than B50. Also 14 strands.
The DF97 was noisy and fast. 14 strands.
The DF97 with the B50 padded loops is quieter and fast. I havn't done a lot with this string yet. Need to try different brace heights and check the results. This string is 8 strands of DF97 and 8 strands of B50 added to the loops. I think this one has the best chance to quiet my Super Mag.
I shoot split finger. I have not shot 3 under, but some guys tell me the noise is different shooting the same bow split versus 3 under. I do put more tension on the middle finger. It makes a duller sound and I usually shoot more accurately (which is why I started doing this).
You could also try padding the limb tips with some light velcro rug where the string contacts the limbs.
Hope this helps. Let us know how it works for you. I sure there are some other tradgangers that can share some ideas also. Take care, Jim