Power Gum?

[Eight Thumbs]

I'm reading John Goddard's book, Trout-Fishing Techniques (2003). It's an interesting read for a number of reasons, not the least of which is the fact that John is from the other side of the pond and gives a different prospective on fishing with the angle. In the section on leaders, John mentions that he likes to use a section of POWER GUM in his hand made leaders. According to John, Power Gum stretches up to 70% of its original length and serves as a shock absorber making it possible to land large fish on light tippets. It also prevents flies from popping off if you hook a branch because of this shock absorbing property.

I regularly read fly fishing catalogs cover to cover and have never seen the stuff. Does anyone use Power Gum? What do you think of the stuff and where can it be obtain? Thanks in advance for any input. 8T