This thread discusses the Content article: Bryce Speed (Butterfly)

Does this rubber have enough dwell time to loop heavy underspin?

I would say yes, but it's a bit harder to handle than its FX sibling. Since switching over to FX on my FH a few weeks ago, my FH loop has improved noticeably. Now I'm using Bryce Speed on my BH, and I am still able to produce the super spinny, slow loops that lower level opponents have no chance against.

In terms of various loops against heavy underspin, it's all down to good technique - you can certainly do it with Bryce Speed. Because it's still a softer rubber than Juic Couga, for example, it's better for looping with control.

I will, however, be using Bryce Speed FX on both FH and BH, when it comes time to renewing them.