What I'm looking for is which of the two lines do people think is the correct height for the average Tsolyáni male? It will affect how large we make the model...
According to the S&G Sourcebook: "A Chlenstands 4 to 5m high at the shoulder." [found under section 1.330]. Compare this to the average Tsolyani , listed under section 1.411, The avg Tsolyani male is 1.68m, while average female is 1.57m. Now, where they mark the end of the "shoulder" of the Chlen. My assumption is the "top" of the Chlen, straight above the forward legs. But. I will refer to those more knowledgeable then I for that conclusion. 4-5m at shoulder height is actually larger then an average Triceritops; which is sometimes compared to the Chlen. http://en.wikipedia.org/wiki/Triceratops
One chlen to Tsolyani image I've found is actually on the foundation site:http://tekumelfoundation.org/images/pic_lc04.jpgWhich, looks more on the lines of "3m" then the original SBook's 4-5m. You may want to ask on the yahoo board if folks think the original SBook reference is a little "off". Just from a practical use perspective, I'd say 3m would be about right. And that seems in that picture to be about the ratio they went for. Anyhow, I think folks with many more years experience with Tekumel should add more on this. Please don't take only my comments for your decision.
In the S&G Player's handbook (p71) the description of the Chlen differs from that in vol 1 (which you reference.) In this description it is 3-4 m high, 5-6 m long from tip to tail. The description also mentions it's weight and forage requirements and other details.
I've always used the 4-5 meter height at shoulder, because I think of the Sourcebook as being the most reliable canon source for such data.Art is always more heavily up to the interpretation of the artist.