A Question for the Blog

Every once in a while, I run across a piece of information that I can't believe I don't know.

Like how to shape a tam.

Since our last discussion (and actually for about a week before that) I've had hats on the brain. I even had a hat on my head last night, believe it or not.

Anyway.

I bought some Regia Silk planning to make a colorwork tam. I sat down to cast on, and realized that I don't really know the first thing about shaping one. All of my knitting resources books are in the US, and I didn't find much online.

I did find a Knitty pattern that seemed reasonably similar to what I want, and it has about a 20% increase in the stitch count right after the ribbing. I did that, but it doesn't seem like nearly enough to me. I'm ok with the decreases part since that's just simple triangle shaping, but how much should I increase on the way up?

Normally I'd just try it and see what happens, but I made the mistake of buying a very fine yarn, so I have about 200 stitches per round. I'm less than inclined to knit the whole thing up and then frog if my number is off, so I'd like to make sure it's ok before I get too far.

Those of you that have knit berets/tams, could you confirm that 20% is a reasonable number? Or perhaps provide a better one? You're also welcome to weigh in if you haven't knit a tam...your guess is as good as mine!

Thanks!