Can you explain a bit more, if you don't mind? From what I've read not being able to port forward can decrease the number of connections you can make while torrenting (i.e. slower down-/upload), but I don't see why this would cause IP leaks assuming your torrent client is configured to only use VPN connections. I've never used it personally. Not trying to be obtuse or anything, I'm just a bit confused and very sceptical in terms of alternatives because I'm not very serious in terms of torrenting and would be hesitant to change my trust.