Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

I wonder how upload is allocated between peers in a private tracker. I noticed that I systematically upload much less than most of the other seeding peers (according to the stats available for a given torrent in the private tracker), even if I am among the first to get a torrent. I also noticed that my max upload speed is much less (e.g. 2MB/s) than what I get with speedtest (e.g. 7MB/s), and it often oscillates between low and high values. I was wondering, is there anything I can do to provide a larger share of upload bandwidth? Does the choice of a torrent client matter? Should I change any specific config? How can I diagnose any bottlenecks from my side? Or is it something completely outside my control? Thanks!