It would be useful knowing which version of aMule is gav616 using, since in my experience, using CVS from May 2nd 2007, aMule does open more slots if needed, my upload is a constant 25kB/s, sometimes just the standard 5 slots with 5kB/s each, sometimes more slots with less upload each, but the fuill 25kB/s are always used.
Regards.