Does Utorrent not allow you to choose the type of header encryption to use? RC4 is the best option bittorrent users currently have available.
Oh and BTW, changing the max_halfopen ports to 90 isn't going to help anything by itself if running on XP (maybe even vista). XP itself has a predisposed limit of
10 halfopen ports per second. Patching the TCP registry entry or using
this patch will help to even things out. (repatch every once in awhile, windows updates tend to reset the TCP to stock settings)
The effect of doing so isn't that great, still. It doesn't have an effect on the amount of peers accumulated in the stack, but allows open connection to more peers at a time. But because of the way bittorrent works, you are still held back by you max upload speed, if you can't give a peer anything, he won't give you anything.