I matched up one of the turns with spy video of the 1er 5-door from a few days ago.
http://youtubedoubler.com/SbQ
You can really see how flat the ft86 is in comparison. I timed them both and they are pretty much identical but the ft86 definitely carries more momentum through the turn. It also sounds like the tires are making pretty much the same noise to my earlier cries of understeer are probably unfounded.
The BMW was practically on 2 wheels on turn in while the ft86 seemed to stay planted.
Here's the turn where I am seeing understeer.
http://youtubedoubler.com/Sg0
Looks like the BMW is able to get itself sorted out and set up for the next turn a lot faster than the Suby
edit... looks like it was just a bad line. The beginning of the video is the same turn and the Suby looks a lot more sorted
http://youtubedoubler.com/Sgi