I'm using a digital fishing scale, similar to the one in the link.
its not as accurate as 0.1 gram but an 1/25 of a pound here or there so i measure everything three times, its good to get an idea about the weight, 44 Kg limit doesnt come cheap.
i hang the airplane on the hook.

http://cgi.ebay.com/40KG-Electronic-...3A1%7C294%3A50