[andrewas]

Its pointless. If your only transfering one file, you will only be using one port. Having extra ones open will do nothing. And if the first one was open, its likely that all the ports in that range are open.

If you have a hardware firewall you might want to look into the settings for it, but I doubt you will be able to do anything to improve the transfer speed. Slow speed could be down to the other persons connection, and remember that upstream speed is generaly significantly slower than downstream speed.