I don't know, the disable_overscan=1 should have done it as far as I know. Does the monitor work without a border on other things? I have a white border of about 1/2 inch but I've only used this monitor with the Pi. It's odd, it appears, then as soon as something covers it up it seems to go away.
tvservice -s probably won't show a lot other than the mode, but you could try tvservice -d > somefile.bin. That should dump the monitor's Extended Display Identification Data (EDID) to a binary file. Then try parse-edid on it. EDID has been through several revisions, so parse-edid doesn't always work. There are some online EDID parsers I think, or other programs to try no doubt. The EDID parsing built into the Pi only works with recent monitors, I have a couple it doesn't work with. My Dell S2409 from 2009 doesn't work with it.
There's also a "roll your own" video mode called CVT, there's a sticky for that at viewtopic.php?f=29&t=24679&hilit=cvt