I know of one person who has. She said that the fish established a hierarchy, and that this suited them. I believe it is best to stock a few females per male so as to discourage male-male fighting.
Personally, I'd advise a larger tank, but if you're going to plant the 10 heavily, then the puffers should have enough definable territory. I'm about to do the same with my 10, and if it works, I'll let you know. I have about 12-15 plants in there of differing sizes in order to provide diversity. However, if you plan on doing that, you need a fertilized substrate, a
CO2 injector and a different type of fluorescent light (18000K). So, up to you, but I'd highly recommend plants or more space. If, everytime, the largest ,male puffer turns around he sees the second-largest male puffer, there will be issues!
Sexing is tough for the IDPs, and I only remember that the underbelly is crucial to determining sex. I believe there is a darker marking on the males... Ah, here we go. Here is a site that explains the sexing (excuse the English-as-a-second-language-ness of the site):
http://www.rr.iij4u.or.jp/~kohda/en/en-dwarfpuffer.htm
Good luck! I'm excited for you. Let me know where you get the IDPs if you do find them. (
www.Aquabid.com sometimes has good deals on them, so you might try there if you can't find them locally.)