XRAY's setup guides are a bit dubious. Elvo's setup guide (that you have already listed) is probably the best one out there - and it is free!

Normally you would expect toe-in to generate stability.

However, a car with driven front wheels will normally be set up with a smidge of toe-out. When you are running, the geometry of the front suspension will make the wheels toe-in back to zero under power, taking out the slack in the linkages. This gives neutral steering response on power, and a little extra steering off power.

Personally I don't bother playing with toe-in on the front end beyond that. Problems with stability are more often a problem with the chassis or radio setup.