Matt,
I'd have thought that forces in the track rods due to negative trail would be insignificant compared to those experienced by a bit of 'lock to lock' when parking, or maybe a few bumps against kerbs by a less than careful driver.
It's a long time since I've driven a 2CV or Dyane backwards at any speed, but from what I recall, as long as the steering wheel was held dead centre there wasn't that much tendency for it to fly out of control.
It was only when you got a bit carried away and tried steering round a corner backwards that things tended to go awry...
Anyway, using the track rods to immobilise the steering isn't a very elegant solution, unless you're building a Cogolin replica ( http://www.flickr.com/photos/derekgottlieb/2459929005/ ), so rather than weld the hub carriers to the arms, this solution below is probably much neater.
That stack of washers at the outer end of the strut can be swapped around to fine tune the toe in or toe out of the wheels, or even compensate for any misalignment resulting from pilot error.
ken
2CV buggy, rear arm detail by slcchassis, on Flickr
realnutter wrote:
there is still negative trail present, so the forces the track rods have to manage are still high...
i've driven enough 2CVs and Dianes to know what happens when you get a bit of lock on, going fast backwards!
Matt