There ain't no making sense of 20 fps gain.
Years back, here on AT, there was Crackers. He had his methods, maybe few strands, smaller diameter servings. optimum timing. He could coax a few fps more. I believe he's still in business.
Still years back, there Ecellerator strings. These were for single cam bows. Said was a gain of 10 fps and maybe more, BUT there was no serving for around the top wheel. Yep, indeed faster, but worries of wear soon had the Ecellerator strings gone. I don't think the lack of serving agreed with double cam bows.
I've played with different size serving and got less fps with thicker serving and more fps with thinner serving. Also, types of serving material will affect speed.
I usually got a loss and gain that stayed around 2 to 3 fps.