You probably won't get an answer on this forum, it's pretty dead. I've got another subforum you'll get more answers at. I won't link it here just in case it's not cool by the rules. Check out my website for more info.
In the mean time, if you haven't seen it there's a gallery of soldier rivers here http://www.turleyknives.com/apps/photos/album?albumid=7626347
Check out the knife descriptions, it'll tell you the stock thickness on the knife pictured. There's 1/8", 5/32", 3/16" and 1/4" s.r.'s in there.