Two things.
1/ passenger is in the wrong spot......look at the starts of races and watch what happens when the passenger moves...sometimes the outfit will lurtch one way or other...depending on the drive.
2/ your entry into the black arts begins (wohahaha) There is more about front ends on sidecars than you will ever know.
Basically though...and others will agree(or not) that it is alot to do with the patch that the front wheel/tyre puts on the ground. Remember it is a sideCAR. Therefore the steering is not a solo anymore and the steering reacts like the front wheel of a car...it rolls over as it turns...and looses contact with the ground. Picture in you mind a solo tyre as you turn...its patch becomes narrower but the length of it stays roughly the same, because as it rolls over the whole wheel goes too. Now picture as sidecar wheel, it doesn't roll over but rather turns up so that the patch actually shortens AND becomes narrower...ooops, no grip!! Very similar to the front of a car hence the wear on the inside front and the need for several wheel alignment methods on the one car.
Therfore and hence, one must drive a sidecar and avoid front end slippage by climbing over the front end and/or sliding through turns much like a quad(which over comes the problem with dual wishbones etc... Is That CLEAR !!
Very good thread on ADV site under Hacks....but you my use up much of your life reading it and the other threads on there