The only way to do it without the ENO Hub (which is a dynomite product, BTW) is to luck out and find a magic ratio, or else file away at your dropouts (not recommended). There is a link that helps find a cog and chainring that will work for a given chainstay length, search for it.

*edit* If you are into that frankensteining isht and don't mind filing, you might also try filing on your axles. If you flatten out the same side of each end, you can get a little bit of adjustability in your vertical drops. Again, like the dropout filing, highly NOT recommended. Just trying to be comprehensive.