Here's a bow I made not too long ago. I think there's enough info with the pics to give you some idea of the dimensions. It has settled in at closer to 62lb@28" now.
http://s96.photobucket.com/albums/l200/62tomsawyer/Asiatic%20Composite%20Bow/http://groups.msn.com/LenniesBowPage/abcwannabes.msnw?Page=1I can tell you that its kind of tough to predict exactly what weight you are going to have as far as poundage. There are a lot of variables. Limb length, limb width, amount of reflex, angle of siyahs, thickness of core, thickness of sinew, thickness of horn. Leave the horn belly over 1/8" thick if you can, because you can tiller with the thickness that way. It works very nicely with a scraper.
I was surprised I didn't get more reflex when I sinewed the bow, but I'm kind of glad it came out this way. It was stout enough as it was. If I do another, I'll probably use a slightly thinner core and slightly more sinew and horn.
One other tip, one of my siyahs is slightly crooked. Pay special attention to lining things up when you do your v-splices, it doesn't take much to get it crooked. The splice cuts weren't crooked, there's just a little play in them so you can get a "leaner" if you aren't careful.
The whole time I was making this bow, I really figured it was jut going to blow up. Amazingly, it has survived and even shoots pretty darn good.