Slow uploads through BIG-IP

It may the that the proxy buffers and receive windows are actually too big. I'd recommend setting the proxy buffers back to 131072, but do increase the receive window to 256 or 512 KB. Send buffer of 1 MB is probably fine.

For the server profile, you can generally use tcp-lan-optimized, unless there is high latency, loss, or congestion expected between the BigIP and the backend servers.

Here's my blog post. I've been able to achieve 100 Mbps uploads and 250 Mbps downloads.