I don't see how fiddling with timeouts can fix anything. It just means the attacker has to apply the exact same attack slightly differently.
For instance, suppose that you have, somewhere on your web-site, a 1 megabyte file. Suppose that you set up your timeouts so that a people have to download at at least 5 KB/s or get cut off (locking out some modem users, but oh well). And suppose that you allow a maximum of 100 Apache worker processes.
If I download that file right at the minimum speed, then I can tie up one of those 100 worker processes for 204.8 seconds. To tie up all 100 of them indefinitely, I have to issue ~1 request every 2 seconds, and use 500 KB/s of bandwidth. That's trivially achievable from a residential connection.
I won't lock other users *quite* as badly as the full slow loris attack -- other connections will get a chance to be serviced once every 2 seconds! -- but it's near as makes no difference in practice.
So fiddling around with header timeouts or whatever might feel good, but isn't going to actually solve the problem, and thus is a waste of time.