Rim uses about 18-20″ of 7x tippet between his two flies. The point fly is an RS2 or Avatar and the upper fly is often a Plebby or a different colored RS2 or Avatar (and usually larger than the point fly). We tie the tippet connecting the two flies on the bend of the hook, which makes it more in line with the next fly.
The other key point is that he was using 0 weight line before there was such a thing. The floating running .027 line is about 60 percent less diameter than a 3 weight line and less than half of the diameter a 5 weight line. This reduces drag dramatically, which is a key to his success, particularly also with the adding of 7x tippets, the fly is also then left free to move naturally in the water. I think those points are more key to why his method is so successful.
I think one of the more interesting points of Rim’s method is that he was the first to offer flies in different colors, of the same pattern. It was common back then that fly patterns came in different sizes, but no one was doing different colors back then, for example an Adams was always grey, which is not always the case today. The RS2 was designed with the idea of six colors and six sizes, which would then allow you a reasonable semblance of matching the prevalent insects in any given stream. This point was also lost on many commercial companies such as Orvis, who offered the RS2 only in grey. Umpqua offered several colors after Rim mentioned it to their higher ups, though he has never been given any royalties by any of the companies who sell RS2s commercially, nor are any of them tied correctly.
There are lots of excellent tippets on the market these days. Rim has used many of them over the years, both fluorocarbon and mono. This is one of his current favorites, but he has never been one to promote various brands, so try for yourself and see what works best.
https://www.rioproducts.com/products/tippet/fluoroflex-plus-tippet
This one is strong and flexible.
For the leader, he still prefers the George Harvey Frog Hair:
http://froghairfishing.com/shop/index.php?route=product/product&path=62&product_id=63
One Fly Fisherman 