The second link I gave you, Curly Purly, is knit in the round so there's no seaming although you do have to graft the crotch. I think you'd have to do that with any pattern though. Problems often arise in patterns when you try to change yarn weight or needle size or adjust the pattern. It's a VERY popular pattern so if you follow the pattern and use the correct weight yarn and needles it should fit just fine. Once you've made it and see how works as written you can play a little bit.