After reading some entries in this forum, I understand that the conventional wisdom is you don't need guides tapering in sizes when building a fly rod. You can just use the smallest guide after the stripper or the tamer.
Here's my question. How do you determine what the smallest size you could use for a particular line? What's the sufficient amount of play inside the ring?
Eijiro Kawada
Tacoma, WA

The rings need to be large enough to pass any required line/leader connections, loops, etc. The line itself takes up very, very little room in even a very small ring or snake. It's getting connections out and back in that can be a problem. The best way to find out, is to tape up a set of guides and try it with the line and connections you plan on using.

The tradition of using all the available sizes and stepping down little by little seems to have arisen out of the fact that whatever the guide makers, produce, people will use. And, may guides are still sold in carded sets. They're set up that way in the sets as well. No need for it, but it's one of those things that has always been done that way.

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Sometimes I do not like to use the same guide size the entire length of the rod. When working out guide spacing and sizes on the tip and second sections of four piece tip-over-butt ferrule blanks, I measure the diameter of the blank beneath the last guide on the tip section, and then find that diameter on the next section. If the blank diameter is smaller where the next guide should go, I step up to the guide size that maintains a straight line through the guides. Because I strive to place the last guide on the ferrule of the tip section, the diameter where the next guide goes on the second section is sometimes quite a bit smaller, but the next guide size larger is as big as I need. I am not concerned abut the loop or ring size of the guide, it is the height off the blank.