Hi Tranduy:
What I do is find the best sprue and really do some " Hot" stretches. Then let it hang by clothes pins on a Hanger over the closet door. That way over time all the natural tendency to curl is gone. You can get real thin that way. If not, Don's suggestion of .05 Mil Monofilament( fishing line) is good for this. I don't work in this scale unless The only version of what I want is only available in 1/700