Apologies if you've read this already because I posted it on the general support forum and was told to try you guys out here

I'm trying to use Transmission 1.54 on Mac (Tiger) to create a torrent file to send to a friend so they can download a chunk of files from me... I'm using OpenBitTorrent as a tracker and it created it fine, checked the file and started seeding. I sent the torrent file to my friend, and it opens in Transmission at his end okay but he can't find me as a peer to download from. I've tried ticking the "Private torrent" box, and having it public, but it doesn't seem to make a difference (I don't understand what it does anyway?!)...
Is it more complicated than this? Or is there a cure?
UPDATE: Since OpenBitTorrent apparently uses UDP which is incompatible with my version of Transmission, I've tried using denis.stalker tracker too, but it appears to be constantly down...
Thanks for your help!
:-Joe