使用IIS上托管的WebServices上传文件 - >最佳实践

We have an application for which UI is built on Flex, and its consuming webservieces built on Dotnet hosted on IIS. we are trying to upload files which are around 100/200 megs , this works like a charm on LAN , if we try to do the same with web service hosted on public ip machines , then this would fail very often(obviously bcoz of lesser bandwidth ) . we have tried increasing executionTimeout(up to 10 minutes) maxRequestLength (up to 200 megs) , this didn't help . so we were thinking what would be the best way to approach this problem , and also what are the best practices which are used in this space.We have an application for which UI is built on