It isn't hard to work out that it's impossible for a forum to maintain a true 1:1 ratio based solely on reported byte counts. First, you have the obvious bootstrapping problem, which is that on day 1, no matter what is uploaded, nobody has any right to download anything because everyone has only uploaded zero bytes.

So you may think "ah, I'll start with an allowance". Just count everyone as having uploaded, let's say for concreteness, 1GB. The next problem is that each file transfer means moving that around like it's money; 1000 bytes downloaded for me is exactly 1000 bytes uploaded by you. But then, again for concreteness, let's say someone puts up a popular torrent and everybody downloads their 1GB directly from this guy. (Imagine they do it in sequence and then don't seed themselves or whatever.) The person with the popular torrent now has all the credit in the system. Then they walk away. Everyone who leaves the system and never comes back, or is just generally unavailable, is taking credit out of the system with them. This is the ongoing problem with the system.

So you must have some sort of mechanism for acquiring "ratio" other than actually uploading something. Fortunately, simply rewarding people for seeding is pretty good. It incentivizes people to seed things that otherwise would be left behind. Even better is to give even more reward for things others aren't seeding. This tends to turn your tracker into a persistent library, with even old things still available, rather than a competition to beat everyone to the popular torrents so that we can download things before everyone else so hopefully we can upload more than we downloaded. I'm sure this isn't perfect but it's a lot better than a rigid ratio system. You just have to deal with people who think it's not "fair" to give out ratio for just hosting things that nobody downloads.